JP2006059416A - Optical disk device and its control method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To effectively prevent a DC offset component when a tracking error signal is obtained by a push-pull method in an optical disk device. <P>SOLUTION: A photodetector 51 for detecting a return light from an optical disk is divided into light receiving parts B and C in the center of a direction orthogonal to a track, and light receiving parts A and D positioned in the outside, and the light receiving parts B and C positioned on the center side are selected and arranged so as not to touch the overlapped part of 0-order and primary diffracted lights contained in the return light. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to an optical disc apparatus and a control method thereof, and more particularly to an optical disc apparatus and a control method thereof in which light is irradiated on the surface of the optical disc and the return light is detected by a photodetector.

  2. Description of the Related Art Conventionally, in an optical disk apparatus, there is an optical pickup apparatus that uses a so-called three spot method in which three light spots are formed along a recording track of an optical disk, and tracking is detected by return light of front and rear light spots. In this apparatus, as shown in FIG. 13, after the laser light emitted from the laser diode 2 is converted into parallel light through the collimator lens 3, the 0th-order light and the first-order light are used using a grating 4 made of a diffraction grating. The main beam and the sub beam are separated. These three lights are reflected by the beam splitter 5 and then slightly tilted with respect to the track of the disk 7 through the objective lens 6 to form three light spots as shown in FIG. The return light obtained by reflecting these three light spots on the disk 7 is transmitted through the beam splitter 5 through the objective lens 6, condensed by the lens 8, and according to the track direction component included in the return light. The light enters the photodetector 9 in which three light receiving portions are arranged corresponding to the three light spots.

  In the photodetector 9, as shown in FIG. 14, the front and rear light receiving portions E and F detect the reflection amounts of the two sub beams to obtain tracking error signals. That is, the two sub beams are opposite to the center of the track, and when the light spot of the main beam deviates from the track, the reflected light amount of each beam changes in the opposite phase as shown in FIG. Accordingly, the tracking error is detected by calculating the difference (EF) in the reflected light amount of the sub-spot.

  However, when a tracking error is detected by the three-spot method shown in FIGS. 13 to 15, it is necessary to dispose a grating 4 (see FIG. 13) in the optical system of the optical pickup device in order to form a sub beam. Moreover, the grating 4 must be adjusted, the optical system becomes complicated, and the output from the laser diode 2 is divided into three, so that the amount of light of the main beam relative to the total amount of light of the laser diode 2 becomes relatively small. Therefore, there is a problem that the utilization rate of laser output is lowered.

  In order to solve such a problem, there is a tracking error detection method using a push-pull method that detects a tracking error with one beam (Japanese Patent No. 338873). FIG. 16 shows the principle of tracking error detection by the push-pull method. In the push-pull method, incident light is diffracted by pits or grooves of an optical disk, and the light intensity distribution in the far field of this diffracted light is divided into two according to the track direction component included in the diffracted light. It is to detect.

  In this method, when the positions of the light beam and the pits or grooves coincide with each other, the light quantity distributions of the light receiving portions E and F of the two-divided photodetector 9 are equal as shown in FIGS. 16 and 17B. As shown in FIGS. 17A and 17C, when the pits, grooves and spots are misaligned, asymmetry occurs in the light quantity distribution of the light receiving portions E and F. In practice, as shown in FIGS. 17A and 17C, when the beam spot is shifted to the left or right with respect to the track, the light amount distributions of the light receiving portions E and F are asymmetric. Moreover, since this asymmetry is reversed depending on the direction of the positional deviation of the spot with respect to the track, the difference E-F is detected by a two-divided photodetector, and time-averaged so that the influence of individual pits is eliminated, Obtain a tracking error signal.

  In such a tracking error detection optical system based on the push-pull method, the grating 4 (see FIG. 13) unlike the tracking error detection system based on the above-described three-spot method is not required. The circuit configuration can be simplified.

  Here, as indicated by a solid line in FIG. 18A, when the optical axis of the objective lens 6 completely coincides with the center of the laser beam reflected upward by the beam splitter 5, it is detected by the photodetector 10. The beam intensity is symmetrical with respect to the center. However, when the objective lens 6 is shaken sideways, the spot moves to the left on the photodetector 10 as shown by a dotted line, for example, and as a result, a DC offset is generated in the push-pull signal itself detected by the photodetector 10. There's a problem.

  The objective lens 6 and the holding plate 11 holding the objective lens 6 are elastically supported in a floating state, and can be moved in the radial direction (left and right in FIG. 18) for tracking servo. Therefore, it can be moved in the optical axis direction for focus servo. In addition, the aperture 12 of the holding plate 11 cuts out the substantially central portion of the laser beam into a circle, and the objective lens 6 and the holding plate 11 having the aperture 12 move. As shown by a dotted line in FIG. 18A, when the optical lens 6 and the holding plate 11 are moved and the light beam of the laser beam cut out by the aperture 12 is in a state indicated by the dotted line, detection on the left side of the photodetector 10 is performed. The intensity increases and the right detection intensity decreases. Therefore, the push-pull signal itself causes a DC offset. When such a DC offset of the push-pull signal is generated, the light spot is controlled to always be offset, and the SN ratio of the recording / reproducing signal of the optical disk is deteriorated.

Next, as shown by a solid line in FIG. 18B, when the surface of the disk 7 is in a posture orthogonal to the laser beam, the reflected light of the disk 7 returns in a state where it matches the aperture 12 of the holding plate 11. And detected by the photodetector 10. Therefore, there is no difference between the left and right detection intensities of the photodetector 10, and no DC offset is generated. However, when the disk 7 is tilted, the laser light reflected by the disk 7 is indicated by a dotted line, so that the left part of the return light cut off by the aperture 12 of the holding plate 11 is lost. From this, although the detection intensity of the left part of the photodetector 10 is not changed, the detection intensity is lowered because a part of the right part is lost. That is, a crescent-shaped missing portion is formed on the right side on the photodetector 10, and the detection intensity is lowered at this portion. Accordingly, in this case as well, there is a problem that an offset is generated in the push-pull signal, whereby the light spot is always controlled to be offset, and the SN ratio of the recording / reproducing signal of the optical disk is similarly deteriorated.
Japanese Patent No. 3381873 Japanese Patent Laid-Open No. 11-25482

  An object of the present invention is to provide an optical disc apparatus capable of obtaining a tracking error signal without using a grating in an optical system, and a control method therefor.

  Another object of the present invention is to provide an optical disc apparatus capable of canceling a direct current component of a tracking error signal generated when an objective lens moves in a radial direction, and a control method thereof.

  Still another object of the present invention is to provide an optical disc apparatus and a control method therefor that can remove a direct current component of a tracking error signal when the optical axis is tilted and the optical axis is shifted.

  Still another object of the present invention is to provide an optical disc apparatus capable of effectively removing a DC offset superimposed on an error signal when a tracking error signal is detected by a push-pull method, and a control method thereof. is there.

  Still another object of the present invention is to obtain a tracking error signal and a focus error signal by combining the outputs of two photodetectors arranged along the optical path of the return light reflected by the optical disk. An optical disk device and a control method thereof are provided.

  The above-described problems and other problems of the present invention will be clarified by the technical idea of the present invention and the embodiments thereof described below.

The main invention of the present application is an optical disc apparatus in which light is irradiated on the surface of the optical disc and the return light is detected by a photodetector.
A first divided region and a second divided region which are divided at a central portion in a direction orthogonal to the return light track; and the first division in a direction orthogonal to the track. A third divided region and a fourth divided region located outside the region and the second divided region, and the first divided region and the second divided region on the center side are 0 of the return light. The present invention relates to an optical disc apparatus characterized in that it does not cover a portion where secondary light and primary light overlap.

Another invention of the present application is an optical disc apparatus in which light is irradiated on the surface of the optical disc and the return light is detected by a photodetector.
A first photodetector and a second photodetector are disposed along the optical path of the return light,
The first photodetector and the second photodetector are respectively divided into a first divided region and a second divided region, which are divided at a center portion in a direction perpendicular to the track of the return light, and a track. A third divided region and a fourth divided region located outside the first divided region and the second divided region in a direction perpendicular to the first divided region, and the first divided region on the center side and The present invention relates to an optical disc apparatus characterized in that the second divided area is not covered with a portion where the zero-order light and the primary light of the return light overlap.

Still another invention of the present application is an optical disc apparatus in which light is irradiated on the surface of an optical disc and the return light is detected by a photodetector.
A first photodetector and a second photodetector are disposed along the optical path of the return light,
The first photodetector has a first divided region and a second divided region which are divided at a central portion in a direction orthogonal to the return light track, and the first divided region in a direction orthogonal to the track. A third divided region and a fourth divided region located outside the one divided region and the second divided region, and the first divided region and the second divided region on the center side are said return Avoid the overlapping of the 0th order light and 1st order light,
The second photodetector is located outside the fifth divided region in the center of the direction orthogonal to the return light track and the fifth divided region in the direction orthogonal to the track. The present invention relates to an optical disc apparatus having a sixth divided area and a seventh divided area.

Still another invention of the present application relates to a method of controlling an optical disc apparatus in which light is irradiated on the surface of an optical disc and the return light is detected by a photodetector.
A first divided region and a second divided region which are divided at a central portion in a direction orthogonal to the return light track; and the first division in a direction orthogonal to the track. A third divided region and a fourth divided region located outside the region and the second divided region, and the first divided region and the second divided region on the center side are 0 of the return light. Avoid the overlapping of the secondary light and primary light,
An optical disc apparatus characterized by canceling a DC component of a tracking error based on a difference between an output of the first divided region and an output of the second divided region, and performing tracking control using a signal in which the DC component is canceled. It relates to a control method.

  Here, the outputs of the first divided area, the second divided area, the third divided area, and the fourth divided area of the photodetector are B, C, A, and D, respectively, and K is a proportionality constant or a function. Then, a tracking error signal may be obtained by (AD) -K (BC).

Still another invention of the present application relates to a method of controlling an optical disc apparatus in which light is irradiated on the surface of an optical disc and the return light is detected by a photodetector.
A first photodetector and a second photodetector are disposed along the optical path of the return light,
The first photodetector and the second photodetector are respectively divided into a first divided region and a second divided region, which are divided at a center portion in a direction perpendicular to the track of the return light, and a track. A third divided region and a fourth divided region located outside the first divided region and the second divided region in a direction perpendicular to the first divided region, and the first divided region on the center side and The second divided area is not covered with the overlapping portion of the zero-order light and the primary light of the return light,
A signal in which the DC component of the tracking error is canceled and the DC component is canceled by a difference between the output of the first divided region and the output of the second divided region of the first photodetector or the second photodetector. Control the tracking by
The present invention relates to a method for controlling an optical disc apparatus, wherein a focus error is detected by a combination of outputs from the first photodetector and the second photodetector, and focus control is performed on the disc based on the focus error. It is.

Still another invention of the present application relates to an optical disc apparatus in which light is irradiated on the surface of the optical disc and its return light is detected by a photodetector, and a control method thereof.
A first photodetector and a second photodetector are disposed along the optical path of the return light,
The first photodetector has a first divided region and a second divided region which are divided at a central portion in a direction orthogonal to the return light track, and the first divided region in a direction orthogonal to the track. A third divided region and a fourth divided region located outside the one divided region and the second divided region, and the first divided region and the second divided region on the center side are the return light. To avoid the overlapping of 0th order light and 1st order light,
The second photodetector is located outside the fifth divided region in the center of the direction orthogonal to the return light track and the fifth divided region in the direction orthogonal to the track. A sixth divided region and a seventh divided region located;
Canceling the DC component of the tracking error due to the difference between the output of the first segmented region and the output of the second segmented region of the first photodetector, and controlling the tracking with the signal canceling the DC component,
The present invention relates to a method for controlling an optical disc apparatus, wherein a focus error is detected by a combination of outputs from the first photodetector and the second photodetector, and focus control is performed on the disc based on the focus error. It is.

  A main invention of the present application is an optical disc apparatus in which light is irradiated on the surface of an optical disc and the return light is detected by a photodetector. The optical detector has a direction perpendicular to the track of the return light. A first divided region and a second divided region divided at the center, a third divided region and a second divided region located outside the first divided region and the second divided region in a direction orthogonal to the track; In addition, the first divided region and the second divided region on the center side are not covered with the overlapping portion of the 0th order light and the first order light of the return light.

  Therefore, according to such an optical disc apparatus, it becomes possible to cancel the direct current component of the tracking error in the direction orthogonal to the track by the difference in output between the first divided area and the second divided area.

Another main invention of the present application is an optical disc apparatus in which light is irradiated on the surface of an optical disc and the return light is detected by a photodetector, and the first photodetector along the optical path of the return light. A first divided region divided by a center portion in a direction perpendicular to the track of the return light, and a first divided region, A second divided area; a first divided area in a direction orthogonal to the track; and a third divided area and a fourth divided area located outside the second divided area; The first divided area and the second divided area are not covered with the overlapping portion of the 0th-order light and the primary light of the return light. Therefore, according to such an optical disc apparatus, the first light The output of the first sub-region of the detector or the second photodetector; It becomes possible to cancel the DC component of the tracking error by the difference in the output of the second divided area and to control the tracking by the signal from which the DC component is canceled. Further, the combination of the outputs of the first photodetector and the second photodetector makes it possible to detect a focus error and perform focus control on the disc based on the focus error.

  Still another main invention of the present application is an optical disc apparatus in which light is irradiated on the surface of an optical disc and the return light is detected by a photodetector. A first photodetector along the optical path of the return light. And a second photodetector, and the first photodetector is divided at the center in the direction orthogonal to the return light track, and the second divided region, A first divided area in the direction perpendicular to the track and a third divided area and a fourth divided area located outside the second divided area; The second divided area is not covered with the overlapping portion of the 0th-order light and the primary light of the return light, and the second photodetector is positioned at the center of the direction orthogonal to the return light track. And a fifth segment in the direction perpendicular to the track. It is obtained to have a sixth divided area and the seventh divided region of which is located outside the region.

  Therefore, according to such an optical disc apparatus, the DC component of the tracking error is canceled and the DC component is canceled by the difference between the output of the first divided region and the output of the second divided region of the first photodetector. Tracking can be controlled by a signal, and a focus error can be detected by a combination of the output of the first light detector and the light output of the second light detection, and the focus control on the disk can be performed based on the focus error. Become.

  The present invention will be described below with reference to embodiments shown in the drawings. FIG. 1 shows an outline of the entire optical disk apparatus according to the present embodiment. This optical disk apparatus includes a spindle motor 21 for driving the optical disk 20, and an optical pickup that optically contacts the optical disk 20. 22 is provided. That is, the optical pickup 22 includes an objective lens 23, a laser light source 24, and a light detection unit 25.

  The optical pickup 22 is moved in the radial direction with respect to the optical disk 20 by a feed motor 28, and this feed motor 28 is connected to a feed servo 29. The optical pickup 22 includes a focus servo 30 and a tracking servo 31.

  An RF signal 34, a tracking error signal 35, and a focus error signal 36 are output from the light detection unit 25 of the optical pickup 22. The RF signal is supplied to the spindle servo 37 and is subjected to signal processing by a signal processing circuit 38 to obtain an output.

  In such an optical disk apparatus, the optical disk 20 is rotated by the spindle motor 21 and the optical pickup 22 is moved in the radial direction of the disk 20 by the feed mode 28 controlled by the feed servo 29. Laser light from the laser light source 24 is irradiated onto the surface of the optical disc 20 through the objective lens 23, and the reflected light is detected by the light detection unit 25 through the objective lens 23. The spindle motor 21 is controlled via the spindle servo 37 based on the RF signal detected by the light detection unit 25. Further, the tracking error signal 35 from the light detection unit 25 is supplied to the tracking servo 31, thereby moving the objective lens 23 in the radial direction and performing tracking control. A focus error signal 36 output from the light detection unit 25 is supplied to the focus servo 30, and the objective lens 23 is controlled in the optical axis direction to perform focus control. The RF signal 34 is processed by a signal processing circuit 38 to obtain a reproduction output.

  Next, the configuration of the optical pickup 22 will be described with reference to FIGS. FIG. 2 shows an optical pickup device using a tracking error detection optical system based on the push-pull method as a whole. The laser light emitted from the laser diode 24 is reflected by the beam splitter prism 41 and is raised. After passing through the four-wavelength plate 42 and converted into parallel light by the collimator lens 43, it is reflected by the rising mirror 44, cut off by the aperture 46 of the holding plate 45, and incident on the optical disk 20 through the objective lens 23. The The return light diffracted by the optical disk 20 is reflected by the rising mirror 44 through the objective lens 23 and the aperture 46, passes through the collimator lens 43 and the quarter wavelength plate 42, and passes through the beam splitter prism 41, and is detected by light shown in FIG. In addition to being incident on the detector 51, it is reflected by the half mirror surface 48, then is reflected by the total reflection surface 49, and enters the photodetector 52. Each of the photodetectors 51 and 52 detects the amount of return light, and obtains an optical signal (RF signal) 34, a tracking error signal 35, and a focus error signal 36 based on the detected light reception output.

  Here, as shown in FIGS. 4A and 4B, the first photodetector 51 and the second photodetector 52 arranged on the half mirror surface 48 of the beam splitter prism 41 at a predetermined distance from each other return light. Are divided into four light receiving portions A to D and E to H, respectively, in accordance with the component in the track direction of the optical disk 20 included in the optical disc 20 so as to receive the return light. In addition, the arrangement of the light receiving parts B, C, and F, G in the photodetectors 51 and 52 is such that the shape for receiving the return light does not cover the overlapping portion of the 0th order light and the primary light included in the return light. Has been selected.

  5A and 5B show another configuration of the photodetectors 51 and 52, where the first photodetector 51 is the same as in FIG. 4A, but the first detector 51 is located on the rear side in the optical axis direction. The second photodetector 52 is configured in three patterns E, F, and G. This is because the tracking error signal is obtained by the first photodetector 51, and the focus error signal is obtained by combining the outputs of the first photodetector 51 and the second photodetector 52. In order to obtain the focus error signal, the photodetector 52 does not need to cut a direct current component and does not divide the central portion F into two.

  In general, the relationship between the superposition of the zero-order light (directly reflected light) and the first-order light (diffracted light) included in the return light when the optical disc 20 is irradiated with the beam spot is shown in FIG. It changes as shown. That is, in a CD (Compact Disc) or MD (Mini Disc) system having a wide track pitch when the diameter of the light spot is constant, the return light diffracted by the optical disc is transmitted in the center in the track direction with zero-order light and A portion where only the 0th-order light is not irradiated does not exist along the direction orthogonal to the track, not on the overlapping portion of the primary light. On the other hand, the track pitch of the optical disk 20 is gradually narrowed. For example, in DVD (Digital Versatile Disc), Blue-ray Disc, HD-DVD, etc., the track pitch is relatively narrower than the spot diameter. For this reason, in the central portion of the return light, there is no overlapped portion of the zero order light and the first order light. If the track pitch of the optical disk 20 is further reduced, the overlapping portion of the zero-order light and the first-order light does not exist completely on the return light spot. In this case, the tracking error cannot be detected by the push-pull method for detecting the primary light.

  This embodiment corresponds to the case where the track pitch is an intermediate pitch in FIG. 9 with respect to the beam spot shape, and the portion where the zero-order light and the primary light do not overlap is in the direction perpendicular to the track. This is the case where it exists in the center of the beam spot. In the present embodiment, the arrangement in which the light receiving portions B and C at the center of the photodetector 51 receive the return light is arranged and shaped so as not to overlap the overlapping portion of the zero-order light and the primary light included in the return light. It is characterized by being selected.

  As described above, the shapes of the light receiving portions B and C of the first photodetector 51 are not applied to the overlapping portions of the 0th-order light and the primary light of the return light, respectively, and have the shape of FIG. 4A. And the difference between the light receiving outputs received by the light receiving portions A and B of the photodetector 51 is AB, and the difference between the light receiving outputs received by the light receiving portions B and C of the photodetector 51 is BC. (See FIG. 10A).

  Here, as described above, the light receiving portions B and C of the photodetector 51 in FIG. 4A are selected to have a shape that does not cover the weight portions of the diffracted light of the 0th order light and the 1st order light in FIG. There is no influence of (primary light). This means that it is not affected by the pits and grooves constituting the tracking signal. Therefore, even if the objective lens 23 moves with respect to the disk 7 or the optical axis 20 is tilted with respect to the beam spot and the optical axis is shifted, canceling the direct current component (offset) BC is as shown in FIG. 10B. The light receiving parts B and C are not affected. Accordingly, a tracking error signal without a DC offset can be detected by calculating a difference BC of the light receiving outputs of the light receiving portions B and C and taking (AD) −K × (BC) ( (See FIG. 10B).

  FIG. 6 shows a circuit for obtaining a tracking error signal based on the outputs of the photodetectors 51 and 52. Here, three subtractors 55, 56 and 57 and a multiplier 58 are combined, whereby the above-described arithmetic expression is obtained. A tracking error signal of (A−D) −K × (B−C) is obtained. A tracking error signal can also be obtained by an arithmetic expression ((A + B) − (C + D)) − K × (BC).

  Further, the focus error signal 36 shown in FIG. 1 can be obtained by combining the outputs of the pair of photodetectors 51 and 52. FIG. 11 shows the light receiving state of the photodetectors 51 and 52 when the objective lens 23 is moved in the optical axis direction and is swung to both sides with respect to the just focus position. The light receiving state forms an image in a shape that is substantially symmetrical with respect to the just focus position.

  Further, the difference between the outputs of the pair of photodetectors 51 and 52 is as shown in FIG. 12, and the difference between the outputs of the pair of photodetectors 51 and 52 becomes almost zero particularly at the just focus position. Therefore, it is possible to detect a positional shift with respect to the just focus depending on how much the difference between the outputs of the pair of photodetectors 51 and 52 has a deviation from 0. This indicates that the focus error signal can be extracted from the difference between the outputs of the pair of photodetectors 51 and 52 arranged along the optical path.

  FIG. 7 shows a circuit for combining the detection outputs of the two photodetectors 51 and 52 of FIGS. 4A and 4B to obtain a focus error signal. That is, here, four adders 61, 62, 63, and 64 and three subtractors 65, 66, and 67 are used, thereby obtaining (A + D) − (B + C) − ((E + H) − (F + G)). I am doing so.

  FIG. 8 shows a circuit configuration for obtaining a focus servo signal based on the outputs of the pair of photodetectors 51 and 52 shown in FIGS. 5A and 5B, and includes three adders 71, 72, 73 and three subtractors 74, 75, 76 is combined. By such a combination, (A + D) − (B + C) − ((E + G) −F) is calculated.

  As described above, by using the photodetectors 51 and 52 having the divided shapes as shown in FIG. 4 or FIG. 5, even when the objective lens 23 moves in the radial direction or the optical axis 20 is tilted and the optical axis is shifted. , Tracking errors without offset can be detected. That is, as described above, the tracking error can be detected by calculating (A−D) −K × (B−C). If the regions B, C and F, G in the central part are selected to have a shape that does not cover the overlapping portion of the 0th order light and the 1st order light, (AD) + (E−H) −K × ((B−C ) + (F−G)) or (E−H) −K × (B−C).

  Further, the difference between the sum A + D of the light receiving outputs of the light receiving portions A and D on both outer sides of the photodetector 51 and the sum B + C of the light receiving outputs of the inner light receiving portions B and C, and the light receiving portion E on both outer sides of the photodetector 52 If the difference between the sum E + H of the light receiving outputs of H and the sum F + D of the light receiving outputs of the inner light receiving portions F and G, that is, (A + D) − (B + C) − ((E + H) − (F + G)) is calculated. Focus error signal can be detected.

  In the above configuration, the return light diffracted by the disk 20 in FIG. 2 is reflected by the rising mirror 44 through the objective lens 23, and passes through the beam splitter prism 41 through the collimator lens 43 and the quarter wavelength plate 42. 3, and after being reflected by the half mirror surface 48, is reflected by the total reflection mirror surface 49 and enters the photodetector 52. Each photodetector 51, 52 detects the amount of incident return light, and obtains an optical signal (RF signal, reproduction output), tracking error signal, and focus error signal from the detected light reception output.

  As shown in FIG. 5B, when a three-segment photodetector having three regions of E, F, and G is used as the photodetector 52 and such a photodetector 52 is combined with the photodetector 51, , (A + D) − (B + C) − ((E + G) −F) can be used to detect a focus error.

  Although the present invention has been described above with reference to the illustrated embodiments, the present invention is not limited to the above-described embodiments, and various modifications are possible within the scope of the technical idea of the invention included in the present application. For example, the above embodiment relates to an optical disk device using the optical disk 20, but the present invention is not limited to the optical disk, and the same effect as the above embodiment can be obtained even when used in a magneto-optical disk device. Can play.

  The present invention can be widely used for tracking servo and focus servo of an optical disc apparatus.

It is a block diagram which shows the whole structure of an optical disk device. It is a principal part longitudinal cross-sectional view which shows the optical system of the optical pick-up of the optical disk apparatus. It is a longitudinal cross-sectional view which shows arrangement | positioning of a pair of photodetector attached to the beam splitter prism. It is a top view which shows the pattern of the light-receiving part of a photodetector. It is a top view which shows another example of the pattern of the light-receiving part of a photodetector. It is a circuit diagram which shows the arithmetic circuit which obtains a tracking error signal from the output of a photodetector. It is a circuit diagram which shows the arithmetic circuit which obtains a focus servo signal from the output of a photodetector. It is a circuit diagram which shows another arithmetic circuit which obtains a focus servo signal from the output of a photodetector. It is explanatory drawing which shows the relationship of superposition of a light beam spot, 0th-order light, and primary light. It is explanatory drawing which shows a tracking error signal and the light reception state of a photodetector. It is a top view which shows the light reception state on a photodetector. It is a graph which shows the change of the detection output of the photodetector at the time of changing a focus state. It is a longitudinal cross-sectional view which shows the optical system for the tracking error detection of the conventional optical disk apparatus. It is a basic diagram which shows the position of the spot in the three spot method, and the pattern of a photodetector. It is a graph which shows the amount of reflected light of each beam in a three spot method. It is a principal part front view which shows the detection principle of the tracking error by a push pull method. It is a top view which shows the detection principle of the tracking error by a push pull method. It is a front view which shows generation | occurrence | production of offset when an objective lens moves and a disk inclines.

Explanation of symbols

2 ... Laser diode, 3 ... Collimator lens, 4 ... Grating, 5 ... Beam splitter, 6 ... Objective lens, 7 ... Optical disc, 8 ... Lens, 9 ... Photo detector, 10 ... 2 Split light detector, 11 ... holding plate, 12 ... aperture, 20 ... optical disc, 21 ... spindle motor, 22 ... optical pickup, 23 ... objective lens, 24 ... laser light source, 25 ... light detection 28, Feed motor, 29 ... Feed servo, 30 ... Focus servo, 31 ... Tracking servo, 34 ... RF signal, 35 ... Tracking error signal, 36 ... Focus error signal, 37 ... Spindle Servo, 38 ... Signal processing, 41 ... Beam splitter prism, 42 ... 1/4 wavelength plate, 43 ... Collimator lens, 44 ... Start up -, 45 ... Holding plate, 46 ... Aperture, 47 ... Substrate, 48 ... Half mirror surface, 49 ... Total reflection surface, 51 ... First photodetector, 52 ... Second light detection 55-57 ... subtractor, 58 ... multiplier, 61-64 ... adder, 65-67 ... subtractor, 71-73 ... adder, 74-76 ... subtractor

Claims (7)

In an optical disc apparatus in which light is irradiated on the surface of an optical disc and the return light is detected by a photodetector,
A first divided region and a second divided region which are divided at a central portion in a direction orthogonal to the return light track; and the first division in a direction orthogonal to the track. A third divided region and a fourth divided region located outside the region and the second divided region, and the first divided region and the second divided region on the center side are 0 of the return light. An optical disc apparatus characterized in that it does not cover a portion where secondary light and primary light overlap. In an optical disc apparatus in which light is irradiated on the surface of an optical disc and the return light is detected by a photodetector,
A first photodetector and a second photodetector are disposed along the optical path of the return light,
The first photodetector and the second photodetector are respectively divided into a first divided region and a second divided region, which are divided at a center portion in a direction perpendicular to the track of the return light, and a track. A third divided region and a fourth divided region located outside the first divided region and the second divided region in a direction perpendicular to the first divided region, and the first divided region on the center side and An optical disc apparatus characterized in that the second divided area is not covered with a portion where the zero-order light and the primary light of the return light overlap. In an optical disc apparatus in which light is irradiated on the surface of an optical disc and the return light is detected by a photodetector,
A first photodetector and a second photodetector are disposed along the optical path of the return light,
The first photodetector has a first divided region and a second divided region which are divided at a central portion in a direction orthogonal to the return light track, and the first divided region in a direction orthogonal to the track. A third divided region and a fourth divided region located outside the one divided region and the second divided region, and the first divided region and the second divided region on the center side are said return Avoid the overlapping of the 0th order light and 1st order light,
The second photodetector is located outside the fifth divided region in the center of the direction orthogonal to the return light track and the fifth divided region in the direction orthogonal to the track. An optical disc apparatus comprising: a sixth divided region and a seventh divided region which are positioned. In a control method of an optical disk apparatus in which light is irradiated on the surface of an optical disk and the return light is detected by a photodetector,
A first divided region and a second divided region which are divided at a central portion in a direction orthogonal to the return light track; and the first division in a direction orthogonal to the track. A third divided region and a fourth divided region located outside the region and the second divided region, and the first divided region and the second divided region on the center side are 0 of the return light. Avoid the overlapping of the secondary light and primary light,
An optical disc apparatus characterized by canceling a DC component of a tracking error based on a difference between an output of the first divided region and an output of the second divided region, and performing tracking control using a signal in which the DC component is canceled. Control method.   When the outputs of the first divided region, the second divided region, the third divided region, and the fourth divided region of the photodetector are B, C, A, and D, respectively, and K is a proportional constant or function, 5. The method of controlling an optical disk apparatus according to claim 4, wherein a tracking error signal is obtained by (AD) -K (BC). In a control method of an optical disk apparatus in which light is irradiated on the surface of an optical disk and the return light is detected by a photodetector,
A first photodetector and a second photodetector are disposed along the optical path of the return light,
The first photodetector and the second photodetector are respectively divided into a first divided region and a second divided region, which are divided at a center portion in a direction perpendicular to the track of the return light, and a track. A third divided region and a fourth divided region located outside the first divided region and the second divided region in a direction perpendicular to the first divided region, and the first divided region on the center side and The second divided area is not covered with the overlapping portion of the zero-order light and the primary light of the return light,
A signal in which the DC component of the tracking error is canceled and the DC component is canceled by a difference between the output of the first divided region and the output of the second divided region of the first photodetector or the second photodetector. Control the tracking by
A control method for an optical disc apparatus, wherein a focus error is detected by a combination of outputs of the first photodetector and the second photodetector, and focus control is performed on the disc based on the focus error. In a control method of an optical disc apparatus in which light is irradiated on the surface of an optical disc and the return light is detected by a photodetector,
A first photodetector and a second photodetector are disposed along the optical path of the return light,
The first photodetector has a first divided region and a second divided region which are divided at a central portion in a direction orthogonal to the return light track, and the first divided region in a direction orthogonal to the track. A third divided region and a fourth divided region located outside the one divided region and the second divided region, and the first divided region and the second divided region on the center side are the return light. To avoid the overlapping of 0th order light and 1st order light,
The second photodetector is located outside the fifth divided region in the center of the direction orthogonal to the return light track and the fifth divided region in the direction orthogonal to the track. A sixth divided region and a seventh divided region located;
Canceling the DC component of the tracking error due to the difference between the output of the first segmented region and the output of the second segmented region of the first photodetector, and controlling the tracking with the signal canceling the DC component,
A control method for an optical disc apparatus, wherein a focus error is detected by a combination of outputs of the first photodetector and the second photodetector, and focus control is performed on the disc based on the focus error.

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