JP2006073049A - Optical pickup controller - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To make appropriate tracking control even when the data recording direction is changed on an optical disk. <P>SOLUTION: The recording on a recording layer is made either from the inner tracks to the outer tracks of an optical disk 10 in the 1st direction or from the outer tracks to the inner tracks in the 2nd direction. One of the two sub-beam spots from the grids LSB is formed in front of the main beam spot from the grid LMB in the tracking direction and the other one in the back of it. When detecting the recording direction change during recording data, the diffraction-grating rotation actuators 13 turns the diffraction-grating 12 around the grid LMB of the main beam spot for a predetermined angle to reverse the positions of the two sub-beam spots against the main beam spot in the recording direction. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to an apparatus for controlling an optical pickup for an optical disk, and more particularly to an optical pickup control apparatus for controlling a spot position of laser light irradiated on an optical disk.

  An optical pickup is known as a device that records and reproduces information by light on an optical disc represented by a CD (compact disc) or a DVD (Digital Versatile Disc). Recently, an optical disc is provided in which a plurality of recording layers are laminated in a single medium.

  In an optical disc, information is recorded along a track of the medium. When recording, reproducing or erasing information, the light spot is focused on the recording surface, and the relative relationship between the light spot and the optical disc is recorded. It is necessary to ensure that the correct displacement is made along the track. Control for focusing the light spot on the recording surface is called well-known “focusing control”. On the recording surface of the disc, a plurality of tracks are formed concentrically around the center of the disc. Control for preventing the light spot from deviating from the track is called “tracking control”, and various methods such as a push-pull method are known. There are various types of tracking control methods, and one “sub-spot method” will be described.

  In sub-spot tracking control, a light beam emitted from a light source of an optical pickup is divided into three light beams of a zero-order light beam and a ± first-order light beam using a diffraction grating, and the zero-order light beam is formed on the recording surface of the optical disk. In this method, a main beam spot is formed, and two sub beam spots with ± primary light beams are formed sandwiching the main beam spot, and a tracking error signal is generated based on the reflected light amount level from the two sub beam spots.

  When data is recorded on a write-once optical disc having a two-layer recording surface, the first layer is the inner track of the disc (hereinafter referred to as the inner track) as in the case of a two-layer DVD-ROM (Read Only Memory). The data is recorded from the outer track to the outer track (hereinafter referred to as the outer track), and the second layer records the data from the outer track toward the inner track. A recording method in which the recording direction is made different for each layer is called an opposite method, while a method for recording both layers from the inner periphery to the outer periphery is called a parallel method.

  Tracking servo under the sub-spot method of write-once optical discs uses a tracking error signal based on the DPP (Differential Push Pull) method, and controls so that the main beam spot is always focused on the track according to the tracking error signal To do.

  An invention relating to the control of such an optical pickup is disclosed in, for example, Patent Documents 1-6. The apparatus of Patent Document 1 has a detector for receiving light from other layers for the purpose of reducing the DPP offset generated by light straying from layers other than the recording layer in the signal recording layer. The component detected by this detector is canceled.

  The apparatus of Patent Document 2 is designed to reduce the DPP offset generated by light straying from a layer other than the recording layer into the signal recording layer so that the sub-beam light amount, the main beam light amount, and the like are appropriate. The diffraction grating pattern formed on the grating has a different period or phase.

  The apparatus of Patent Document 3 corrects the position shift of the sub beam spot caused by the variation in the thickness of the optical disk by correcting the position of the objective lens and the displacement of the diffraction grating.

  In order to reduce various interferences in the optical pickup, the device of Patent Document 4 arbitrarily changes the directions of the long axis and the short axis of the light spot by rotating a phase difference plate (Phase Panel).

Patent Document 5 shows a technique related to a pickup configuration corresponding to a multi-wavelength LD (Laser Diode). Patent Document 6 discloses a technique related to detection and switching of a focus error signal.
JP 2003-67949 A JP 2003-162832 A JP 2002-25082 A JP 2002-230822 A JP 2004-158118 A JP 2002-190132 A

  The opposite method is adopted in most of the current commercially available dual-layer DVD-ROMs, and improvement in scanning performance and accuracy is desired. However, when recording data on a disc according to the opposite method, a tracking offset that does not occur during recording from the inner circumference of the first layer toward the outer circumference is directed from the outer circumference of the second layer to the inner circumference due to a change in light reflectance. It occurred during recording, and it was difficult to properly perform tracking control when recording data on the second layer. This will be described with reference to FIGS.

  In FIG. 9, in the two-layer optical disc 10, the first layer 81 is a pit indicating data in an opposite manner from the inner periphery to the outer periphery indicated by the arrow 30, and the second layer 82 is an opposite method from the outer periphery to the inner periphery indicated by the arrow 31. The state of recording 60 is schematically shown.

  A situation in which the pit 60 is recorded on the first layer 81 in FIG. 9 is schematically shown in FIG. 10, and a situation in which the pit 60 is recorded on the second layer 82 is schematically shown in FIG. As shown in FIGS. 10 and 12, in each recording layer of the optical disc 10, grooves 41 and lands 51, which are data recording tracks, are alternately formed in a concentric manner with respect to the center of the optical disc 10. . The groove 41 is a convex portion into which data is written as the pit 60, and address information indicating the current position is written in advance in the groove 41, and data should be written based on this address information at the time of writing. The position is specified. Address information is recorded at a plurality of predetermined positions on the flat land 51 between the grooves 41.

  Referring to FIG. 10, pit 60 is formed in first layer 81 by moving main beam spot MB on groove 41 in the tracking direction indicated by arrow 70. The size of the pit 60 varies depending on the amount of information. The pit 60 has a shape that rises due to a chemical change caused by irradiating the film of the organic dye material of the groove 41 with the main beam. Here, the sub beam spots SB1 and SB2 are located on both lands 51 adjacent to the groove 41 where the main beam spot MB is located (at a position sandwiching the main beam MB). The main beam spot MB and the sub beam spots SB1 and SB2 are positioned substantially in parallel, and one of the sub beam spots SB1 and SB2 is located in front of the main beam spot MB (a position that matches the direction of the arrow 70), and the other is the main beam spot. It is in the rear position (position opposite to the direction of the arrow 70) with respect to the beam spot MB.

  At the time of data recording, reflected light from the main beam spot MB and the sub beam spots SB1 and SB2 is detected by a photodetector provided in the optical pickup, and a tracking error signal is generated based on the detected amount of received light. FIG. 14 shows an outline of the light receiving surface of the photodetector that receives the reflected light from the main beam spot MB and the sub beam spots SB1 and SB2.

  The photodetector in FIG. 14 has a light receiving surface 151 for the main beam spot MB and light receiving surfaces 152 and 153 for the sub beam spots SB1 and SB2. The light receiving surface 151 is divided into four partial surfaces A, B, C and D, the light receiving surface 152 is divided into partial surfaces E and F, and the light receiving surface 153 is divided into partial surfaces G and H. Here, the received light amount of each partial surface is indicated by the reference symbol A-F of the corresponding partial surface.

  Returning to FIG. 10, a signal MPP (Main Push Pull) is derived as shown in FIG. 11 using the received light amounts of the four portions of the main beam spot MB corresponding to the four light receiving surfaces A-D. FIG. 11 shows five types of signals when the tracking control is OFF, the vertical axis indicates the amplitude level (unit: voltage), and the horizontal axis indicates time (unit: second). Since the signal MPP in FIG. 11 is calculated according to (A + B) − (C + D) with respect to the amount of received light, the degree of deviation of the main beam spot MB from the groove 41 is indicated by the signal MPP. The tracking control is such that the level of the signal MPP is zero, in other words, the main beam spot MB follows the groove 41.

  The signal SPP (Sub Push Pull) of FIG. 11 is derived by SPP = (E−F) + (GH) using the received light amounts of the light receiving surfaces E−H of the sub beam spots SB1 and SB2 of FIG. Then, the signal DPP is derived by using the signal MPP and the signal SPP (MPP-K × SPP: where the constant K is a value uniquely determined by the optical pickup). A signal DPP indicates a tracking error signal. The tracking control is performed based on the tracking error signal so that the main beam spot MB is always focused on the track (on the groove 41).

  At the time of data recording of the first layer 81, as shown in FIG. 10, the reflected light of the sub beam spot SB1 is blocked by the pits 60 already formed in both adjacent grooves 41 (because the reflectivity decreases). ) Since the received light levels of the partial surfaces G and H are approximately uniform, and the reflected light of the sub beam spot SB2 has not yet been formed with the pits 60 in both adjacent grooves 41, the received light levels of the partial surfaces E and F are Approximately uniform. Therefore, the signal SPP does not include an offset due to the change in the amount of reflected light of the sub-beam spots SB1 and SB2, and therefore the signal DPP does not include any offset component. Therefore, tracking control according to the tracking error signal of the signal DPP can be properly performed.

  Now, when the recording layer is switched to the switching second layer 82, it is as shown in FIGS. In FIG. 13, signals of the same type as described in FIG. 11 when tracking control is OFF are taken (the amplitude (unit: voltage) on the vertical axis and time (unit: second) on the horizontal axis for each signal in FIG. 13). It has been. Referring to FIG. 12, at the time of data recording on the second layer 82, with respect to the sub beam spot SB1 adjacent to the main beam spot MB, the pit 60 is already formed in the groove 41 on the outer peripheral side of the disc. Since the pit 60 is not formed at 41, a difference occurs in the received light amount levels of the partial surfaces G and H. Similarly, with respect to the sub beam spot SB2, one of the adjacent grooves 41 has the pit 60 formed but the other is not formed, so that the difference in the received light level between the partial surfaces E and F also occurs. Therefore, since SPP = (E−F) + (G−H), the signal SPP includes an offset 80 from the reference level LV due to the difference in the amount of received light as shown in FIG. Thus, the offset is also included in the signal DPP. Therefore, it becomes difficult for the second layer 82 to perform preferable tracking control due to the offset.

  Thus, at the time of data recording according to the sub-spot method and the opposite method, the signal DPP includes an offset caused by a change in the amount of reflected light at the sub-beam spot, making it difficult to perform proper tracking control. However, Patent Documents 1 to 6 described above do not show any configuration for eliminating such an offset that occurs during data recording.

  SUMMARY OF THE INVENTION Therefore, an object of the present invention is to provide an optical pickup control device that enables appropriate tracking control even when the data recording direction on an optical disk is switched.

According to an aspect of the present invention, a light beam from a light source is split into three light beams of a zero-order light beam and a ± first-order light beam by a diffraction grating portion on a recording layer of an optical disc in which a plurality of tracks are formed concentrically. The main beam spot is formed by the zero-order light beam and two sub beam spots are formed by the ± first-order light beam so as to sandwich the main beam spot, and the main beam spot is formed on the track. The positional relationship of the gratings for the 0th-order light beam and the ± 1st-order light beam of the diffraction grating portion and the positional relationship of the main beam spot and the two sub-beam spots in the recording layer match, The tracking error signal of the tracking control is obtained based on the amount of reflected light of the two sub beam spots. ,
The recording direction in the recording layer is either the first direction from the inner track to the outer track or the second direction from the outer track to the inner track, and one of the two sub beam spots is in the tracking direction. The other is formed in front of the main beam spot and the rear,
The optical pickup control device comprises:
A recording direction change detecting means for detecting that the recording direction has changed during data recording;
When the change in the recording direction is detected by the recording direction change detecting means, the diffraction grating portion is set at a predetermined angle so as to reverse the positions of the two sub beam spots with respect to the main beam spot before and after the change in the recording direction. Diffraction grating rotating means for rotating around the grating of the main beam spot.

  Therefore, when the recording direction is changed, the position of the two sub beam spots with respect to the main beam spot is reversed by rotating the diffraction grating portion around the grating of the main beam spot, that is, on the track by the main beam spot. Under the influence of the pits of the recorded data, the sub beam spot is formed at a position where the reflectance of light is not uniform in the same sub beam spot but becomes substantially the same.

  Therefore, even when the tracking control tracking error signal is obtained based on the reflected light amounts of the two sub-beam spots, the tracking error signal does not include an offset component due to non-uniform light reflectance. This makes it possible to perform appropriate tracking control.

Preferably, the optical disc comprises a plurality of recording layers,
The change in the recording direction indicates that the recording layer to be recorded has changed from one recording layer to another recording layer.

  Therefore, even if an opposite method is adopted in which the recording direction is reversed in each layer adjacent to the optical disk having a multi-layer recording layer, the diffraction grating portion is made to change the grating of the main beam spot when the recording layer is changed, as described above. By rotating around the center, the tracking error signal can be prevented from including an offset component due to non-uniform reflectance of the light of the two sub beam spots for obtaining the tracking error tracking error signal. Appropriate tracking control can be performed using the signal.

  Preferably, address information indicating a recording position read from the track at the time of data recording is compared with address information corresponding to each of the plurality of recording layers, and based on a comparison result, the recording layer to be recorded is recorded. Recording layer discrimination means for discriminating changes is further provided.

  Preferably, the apparatus further includes a rotation angle determination unit that determines the predetermined angle.

  Preferably, the sub beam spot is formed in a region disposed between the concentrically formed tracks, and the predetermined angle includes a distance between the main beam spot and the sub beam spot, and 2 adjacent to the track. And the distance between the two regions.

  According to another aspect of the present invention, a light beam from a light source is separated into a zero-order light beam and a ± first-order light beam by a diffraction grating portion on a recording layer of an optical disk in which a plurality of tracks are formed concentrically. The main beam spot is formed on the track by irradiating and forming a main beam spot with the zero-order light beam and forming two sub-beam spots with the ± first-order light beam sandwiching the main beam spot. The data is recorded in accordance with the above, and the positional relationship of the gratings for the zero-order light beam and the ± first-order light beam of the diffraction grating portion and the positional relationship of the main beam spot and the two sub beam spots in the recording layer are one. The tracking error signal for tracking control is the control method of the optical pickup obtained based on the reflected light quantity of the two sub beam spots. It is as follows.

  The recording direction in the recording layer is either the first direction from the inner track to the outer track or the second direction from the outer track to the inner track, and one of the two sub beam spots is tracking. The other is formed in front of the main beam spot and the other in the rear.

The control method of this optical pickup is
A recording direction change detection step for detecting that the recording direction has changed during data recording;
When a change in recording direction is detected by the recording direction change detecting step, the diffraction grating portion is set at a predetermined angle so as to reverse the positions of the two sub beam spots with respect to the main beam spot before and after the recording direction change. A diffraction grating rotation step for rotating the grating around the main beam spot.

  Embodiments of the present invention will be described below with reference to the drawings. Here, it is assumed that data is recorded on an optical disc having two recording layers according to the sub-spot method and the opposite method. Then, tracking control is performed using the tracking error signal of the DPP signal obtained at the time of data recording. Although the number of recording layers is two here, it may be three or more.

(Configuration of optical pickup)
Referring to FIG. 1, an optical pickup (hereinafter abbreviated as PU) 64 according to an embodiment of the present invention includes a semiconductor laser 11 as a light source, a diffraction grating 12, a diffraction grating rotation actuator 13, a collimating lens 14, and light detection. And an actuator 21 for the objective lens 20, a condenser lens 16, a beam splitter 17, a quarter-wave plate 18, a rising mirror 19, an objective lens 20 and an objective lens 20. The objective lens 20 adjusts the focusing position on the recording surface of the laser beam. The actuator 21 controls the focal length of the objective lens 20 by adjusting the position of the objective lens 20 according to a given signal. Thus, the actuator 21 is used to perform focus servo for focusing control. Although not described in detail here, the actuator 21 also adjusts the position of the objective lens 21 for tracking control.

  In operation, light emitted from the semiconductor laser 1 is transmitted through the diffraction grating 12 and separated into a zero-order light beam passing through the grating LMB and a ± first-order light beam passing through the gratings LSB on both sides. These three light beams are converted into substantially parallel light beams by the collimator lens 14, pass through the beam splitter 17, pass through the quarter-wave plate 18, and are converted from linearly polarized light to circularly polarized light, and a rising mirror 19. The light is condensed by the objective lens 20 and is imaged as three light spots on the recording surface of the optical disc 10. The optical disk 10 is configured such that two recording layers, a first layer 81 and a second layer 82, are overlapped.

  Of these light spots, the main beam spot MB is based on the 0th-order light beam, and the sub-beam spots SB1 and SB2 are based on the ± first-order light beam. The two sub beam spots SB1 and SB2 are positioned so as to sandwich the main beam spot MB. Each light beam imaged as a light spot is returned as a reflected light when reflected on the recording surface, passes through the objective lens 20, returns to a substantially parallel light beam, and passes through the quarter-wave plate 18. As a result, the light passes through the quarter-wave plate 18 twice, so that the first laser beam is converted to polarized light whose deflection surface is rotated by 90 degrees, that is, returns to linearly polarized light. All of this linearly polarized light is reflected by the beam splitter 17, and then passes through the condenser lens 16 and enters the photodetector 15.

  As shown in FIG. 14, the photodetector 15 is separated into a partial surface A-D that receives the return light from the main beam spot MB and a partial surface E-H that receives the return light from the sub beam spots SB1 and SB2. Yes. A focus error signal for “focusing control” is generated by a known procedure based on the received light amount level on the partial surface A-D.

(Change of sub beam spot position)
In the present embodiment, by controlling the PU 64 of FIG. 1, it is possible to avoid including an offset in the tracking error signal as in the prior art even if the recording target layer changes. This can be achieved by changing the positions of the sub beam spots SB1 and SB2 with respect to the main beam spot MB when the recording target layer changes. This will be described with reference to FIGS. 4 and 5 show the state at the time of data recording on the first layer 81 in the same manner as in FIGS. 6 and 7 show the state at the time of data recording on the first layer 82 in the same manner as in FIGS.

  As described above, when the recording target layer is changed, the recording direction is changed in the opposite method. Therefore, in the present embodiment, as shown in FIGS. 4 and 5, when recording the first layer 81, the partial surfaces E and F have the same reflectance and the partial surfaces G and H have the same reflectance as in the conventional case. No offset occurs. At the time of recording on the second layer 82, the positions of the sub beam spots SB1 and SB2 with respect to the main beam spot MB are moved to positions different from the positions shown in FIG. In FIG. 6, the sub-beam spot SB1 has substantially the same light reflectance at the partial surfaces E and F due to the pits 60 recorded in the grooves 41 on both sides, and the sub-beam spot SB2 has no pits 60 recorded in the grooves 41 on both sides. Accordingly, the reflectance of light on the partial surfaces G and H is also substantially the same, and the offset 80 does not occur in the differences (E−F) and (G−H) shown in FIG. Therefore, the signal DPP of FIG. 7 as the tracking error signal TE does not include the offset 80 as shown in FIG. 13, and preferable tracking control can be performed using the tracking error signal TE.

  Here, the movement of the sub beam spots SB1 and SB2 in the direction of the arrow 84 is realized by rotating the diffraction grating 12 by the diffraction grating rotating actuator 13 in a predetermined direction according to the arrow 84 by a predetermined angle. FIG. 8 shows a procedure for determining an angle for rotating the diffraction grating 12. The solid line sub-beam spots SB1 and SB2 in FIG. 8 indicate the positions of the sub-beam spots (the positions shown in FIG. 4) when the first layer 81 is the recording target layer, and the broken line sub-beam spots SB1 and SB2 The position of the sub beam spot (position shown in FIG. 6) when it is the recording target layer is shown. A line segment connecting the solid beam sub-spots SB1 and SB2 and the center of the main beam spot MB is a straight line L1, and a line segment connecting the broken beam sub-beam spots SB1 and SB2 and the center of the main beam spot MB is a straight line L2. The above-described offset does not occur when the sub beam spots SB1 and SB2 are positioned on L1 and when the sub beam spots SB1 and SB2 are positioned on the straight line L2.

  As shown in FIG. 8, for example, when the recording target layer is changed from the first layer 81 to the second layer 82, the straight line L1 is rotated by an angle 2α in the direction of the arrow 92 around the center point CP of the main beam spot MB. Thus, the straight line L1 moves to the position of the straight line L2. In other words, the solid sub-beam spots SB1 and SB2 move to the positions of the broken sub-beam spots SB1 and SB2. Conversely, when the recording target layer is changed from the second layer 82 to the first layer 81, the straight line L2 is rotated about the center point CP of the main beam spot MB by an angle 2α in the direction opposite to the arrow 92, The straight line L2 moves to the position of the straight line L1. In other words, the wavy sub beam spots SB1 and SB2 move to the positions of the solid sub beam spots SB1 and SB2.

  As described above, when the recording target layer changes between the first layer 81 and the second layer 82, that is, when the recording direction changes between the recording directions indicated by the arrows 30 and 31, the straight line L1 or L2 is set at the center point CP. It is only necessary to rotate it by an angle 2α around the center.

  By the way, the positional relationship between the main beam (zero-order light beam) and the sub beam (± first-order light beam) after passing through the diffraction grating 12, that is, the positional relationship between the main beam and the sub beam immediately after passing through the diffraction grating 12, is the optical system of FIG. Since the position of the corresponding spot (main beam spot MB and sub-beam spots SB1 and SB2) generated by forming an image on the recording target layer through the line coincides with the position of the line L2 by rotating the straight line L1. To move the diffraction grating 12 by an angle 2α without changing the inclination of the plane having the gratings LMB and LSB around the grating LMB in the direction corresponding to the direction of the arrow 92, that is, in the direction of the arrow 22 You can do it.

  Therefore, by rotating the diffraction grating 12 by a predetermined angle 2α in a predetermined direction, it is possible to place the sub beam spots SB1 and SB2 at positions where the offset 80 does not occur. The angle 2α is determined based on a distance (constant) 91 between adjacent lands 51 in the optical disc 10 and a distance (constant) 90 between the main beam spot MB and each sub beam spot as shown in (Expression 1). Can do. The distance 90 is uniquely determined by the specifications of the PU 64, and the distance 91 is uniquely determined by the specifications of the optical disk 10.

sin α = (distance 91/2) / distance 90 (Expression 1)
(Configuration of optical disc recording / reproducing apparatus)
Referring to FIG. 2, the optical disc recording / reproducing apparatus according to the present embodiment equipped with PU 64 of FIG. 1 rotates PU 64 and optical disc 10 that emit laser light to optical disc 10 and receive reflected light from optical disc 10. Spindle motor 65 to be driven, spindle drive circuit 77 to drive the spindle motor 65, tracking drive circuit 75 to drive an actuator (not shown) that performs tracking servo of the PU 64, and focus drive circuit to drive the actuator 21 that performs focus servo of the PU 64 74, a sled 66 for moving the PU 6 in the radial direction of the optical disc 10, and a sled drive circuit 76 for driving the sled 66.

  Further, the optical disk recording / reproducing apparatus inputs an reproduction signal (read signal) from the optical pickup 3 based on the recording data on the optical disk 10, generates an RF (Radio Frequency) signal from the reproduction signal, and amplifies the RF amplifier 78. A reproduction signal processing unit 63 that inputs and processes an RF signal from the RF amplifier 78 and outputs a video signal and an audio signal is provided.

  Further, the optical disc recording / reproducing apparatus includes a tracking error detection circuit 71 for detecting the tracking error signal TE included in the RF signal from the RF amplifier 78, and a focus error for detecting the focus error signal FE included in the RF signal. A detection circuit 72 and a rotation actuator circuit 73 for controlling the diffraction grating rotation actuator 13 of FIG. 1 are provided.

  Further, the optical disc recording / reproducing apparatus includes a CPU 61 for controlling and monitoring the entire apparatus, a memory 79 for storing various data and programs, a control circuit 67 for controlling each circuit according to the CPU 61, and a video signal given from the outside. And a recording signal processing unit 62 that performs processing of converting the audio signal into a signal for recording on the optical disc 10 and outputs a signal of the processing result to the PU 64.

  The memory 79 stores layer address data 79, type data 87, a land-to-land distance table 88, and spot-to-spot distance data 91. The type data 87 indicates the type of the optical disc 10. The inter-land distance table 88 is a table that stores data of the distance 91 between the lands 51 of the optical disk 10 of the type corresponding to each of the plurality of types of the optical disk 10. The inter-spot distance data 90 indicates the distance 90 of FIG.

  The control circuit 67 includes a rotation amount determination unit 68 that determines and outputs a rotation direction and a rotation amount for rotating the diffraction grating 12 and a layer determination unit 69 that determines a layer to be recorded on the optical disc 10. The rotation actuator circuit 73 generates a signal RS based on the output of the rotation amount determination unit 68 and supplies the signal RS to the diffraction grating rotation actuator 13. Since the diffraction grating rotation actuator 13 drives the diffraction grating 12 according to the given signal RS, the diffraction grating 12 rotates in the direction determined by the rotation amount determination unit 68 by the same determined angle. Thereby, as shown in FIG. 1, the diffraction grating 1 rotates around the grating LMB without changing the inclination of the plane including the gratings LMB and LSB.

  The diffraction grating 12 is rotated by the diffraction grating rotation actuator 13 as follows, for example. That is, assuming that the diffraction grating rotary actuator 13 includes an ultrasonic motor element, the diffraction grating rotary actuator 13 is provided in association with the diffraction grating 12 by exciting the piezoelectric element of the ultrasonic motor element in accordance with the input signal RS. Since a higher-order bending vibration is generated on the surface of the elastic vibrating body (stator) and a traveling wave is generated, a slider provided on the diffraction grating 12 for rotating the diffraction grating 12 is pressure-bonded to the stator with a constant pressure. Thus, the slider is driven by the frictional force generated between the slider and the stator. As a result, the diffraction grating 12 rotates by a predetermined angle in a predetermined direction of the traveling wave generated based on the signal RS. The method of rotating the diffraction grating 12 by the diffraction grating rotation actuator 13 is not limited to this. For example, when a shaft sliding type actuator is used as the diffraction grating rotary actuator 13, each coil is provided at both ends of the diffraction grating 12, and a permanent magnet is provided at a fixed portion on the diffraction grating rotary actuator 13 side. The diffraction grating 12 may be rotated by changing the magnetic flux direction.

  With reference to FIG. 3, a control procedure for recording data on the optical disc 10 will be described. The program according to the flowchart shown in FIG. 3 and various data referred to for executing the program are stored in the memory 79 in advance, and the control procedure is realized by the CPU 61 reading and executing the program and referring to the data as appropriate. Is done. At the start of the flowchart of FIG. 3, the diffraction grating 12 is in an initial state. This initial state is a state in which a light beam spot is formed on the straight line L1 in FIG.

  First, when the optical disk 10 is set in the optical disk recording / reproducing apparatus of FIG. 2 so as to be rotatable by the spindle motor 65, the CPU 61 performs a process for determining which layer is to be recorded (step S ( Hereinafter, simply abbreviated as S) 3).

  Specifically, when the CPU 61 detects that the optical disk 10 is set in the data recording mode, the CPU 61 drives the spindle motor 65 via the spindle drive circuit 77 to rotate the optical disk 10, and via the thread drive circuit 76. The sled 66 is driven to move the PU 64 to a position corresponding to a predetermined position on the optical disk 10. It is assumed that the CPU 61 has previously obtained information for specifying the predetermined position. Then, since the reproduction signal processing unit 63 is instructed to output a reproduction signal to the PU 64, the reproduction signal processing unit 63 drives and controls the semiconductor laser 11 to emit a laser beam for reproduction. The reflected light from the laser light irradiated to the region at the predetermined position is derived as an RF signal by the RF amplifier 78 via the photodetector 15 and processed by the reproduction signal processing unit 63. The processing result signal includes data indicating the type of the optical disk 10 recorded in an area at a predetermined position and address information, and is provided to the CPU 61. The address information indicates address information at which data recording is to be started, address information corresponding to the first layer, and address information corresponding to the second layer 82. The CPU 61 stores data indicating the type of the optical disk 10 indicated by the input processing result signal in the memory 79 as type data 87, and stores address information indicated by the processing result signal in the memory 79 as layer address data 86.

  The CPU 61 reads the layer address data 86 from the memory 79 and gives it to the control circuit 67 as a control signal. The layer determination unit 69 of the control circuit 67 determines whether the layer to be recorded is the first layer 81 or the second layer 82 based on the given control signal.

  That is, the recording start address information indicated by the control signal is compared with the corresponding address information in the first layer 81 and the corresponding address information in the second layer 82 indicated by the control signal, and the recording is performed based on the comparison result. It is determined whether the start address information corresponds to the address information of the first layer 81 or the second layer 82, and the recording target layer is specified based on the determination result. Data indicating the specified recording target layer is stored as layer data 85 in an internal memory (not shown) of the control circuit 67.

  Thereafter, each unit is set to a state for starting recording (S5). When the layer data 85 indicates the first layer 81, the diffraction grating 12 should be in the initial state. However, since the diffraction grating 12 is in the initial state here, the rotation amount determination unit 68 sends the control signal to the rotary actuator circuit. No output to 73.

  On the other hand, when the layer data 85 indicates the second layer 82, the rotation amount determination unit 68 determines the rotation direction and the rotation angle 2α indicated by the arrow 92 based on the layer data 85, and outputs the determination result to the rotary actuator circuit 73. To do. The rotation actuator circuit 73 generates a signal RS based on the output from the rotation amount determination unit 68 and outputs the signal RS to the diffraction grating rotation actuator 13. The diffraction grating rotation actuator 13 rotates the diffraction grating 12 in the determined direction by the determined angle based on the given signal RS.

  The angle 2α is obtained as follows. The CPU 61 searches the inter-land distance table 88 based on the type of the optical disk 10 indicated by the type data 87 of the memory 79 to identify and read out the data of the corresponding distance 90, and gives it to the rotation amount determination unit 68. Further, the CPU 61 reads the spot distance data 91 from the memory 79 and gives it to the rotation amount determination unit 68. Thereby, the rotation amount determination unit 68 obtains the rotation angle 2α based on the equation (1) using the data of the distance 90 and the spot distance data 91 given from the CPU 61.

  The control circuit 67 controls the actuator 21 via the focus drive circuit 76 based on the layer data 85. Thus, the laser light is set to be focused on the determined recording target layer via the objective lens 20.

  Thereafter, the CPU 61 controls the control circuit 67 so as to drive the optical disc 10 and the PU 64 via each drive circuit (S7), and the recording signal processing unit 62 outputs the data signal for recording outputted therefrom to the PU 64. (S9). As a result, the semiconductor laser 11 of the PU 64 emits a laser beam in accordance with a given data signal.

  During recording, the photodetector 15 outputs a signal based on the amount of reflected light from the main beam spot MB and the sub beam spots SB1 and SB2 to the RF amplifier 78, so that the RF signal is output from the RF amplifier 78 to the tracking error detection circuit 71 and the focus. It is output to the error detection circuit 72 and the control circuit 67. Accordingly, the tracking error detection circuit 71 and the focus error detection circuit 72 output the tracking error signal TE and the focus error signal FE. Tracking control and focusing control are performed based on the output tracking error signal TE and focus error signal FE.

  The layer discriminating unit 69 of the control circuit 67 inputs an RF signal, and the layer currently being recorded is the first layer 81 and the first layer based on the address information included in the input RF signal, that is, the address information read from the groove 41. Which of the two layers 82 is determined is determined. That is, the read address information is compared with each of the address information corresponding to the first layer 81 and the address information corresponding to the second layer 82 indicated by the layer address data 86 read from the memory 79 by the CPU 61. Discriminate based on the result. While this determination result indicates that the layer is the same as the layer indicated by the pre-recorded layer data 85 (NO in S11), the processes in steps S7 and S9 are repeated.

  On the other hand, when the determination result indicates that the layer is different from the layer indicated by the layer data 85 (YES in S11), the recording operation is paused by updating the layer data 85 to indicate the layer indicated by the determination result. (S13). That is, since the control circuit 67 notifies the CPU 61 that the layer has been changed based on the determination result, in response to the notification, the CPU 61 causes the recording signal processing unit 62 to transmit the light beam based on the recording data from the semiconductor laser 11. Control is performed so that a light beam for reproduction is irradiated instead of irradiation (S13).

  Thereafter, the rotation amount determination unit 68 determines the rotation direction and the angle 2α of the diffraction grating 12 based on the layer indicated by the layer data 85 (S15). Specifically, when the layer data 85 indicates the first layer 81, a signal that rotates the straight line L2 in FIG. 8 by an angle 2α in the direction opposite to the direction of the arrow 92 and is positioned on the straight line L1 is generated and output. When the data 85 indicates the second layer 82, a signal is generated and output so that the straight line L1 in FIG. 8 is rotated by an angle 2α in the direction of the arrow 92 and positioned on the straight line L2. The angle 2α can be calculated according to (Equation 1). Since the output signal is given to the rotary actuator circuit 73, the rotary actuator circuit 73 generates a signal RS based on the given output signal and gives it to the diffraction grating rotary actuator 13 of the PU 64. The diffraction grating rotation actuator 13 rotates the diffraction grating 12 in the direction of the arrow 22 in FIG. 1, for example, according to the direction based on the given signal RS and the angle 2α (S17).

  Thereby, when the recording target layer is changed during data recording, the light beam emitted from the semiconductor laser 11 and output through the diffraction grating 12 passes through the position rotated in the direction of the arrow 221 in the collimator lens 14, and the optical disk 10. , A light spot is formed at a position moved in the direction of the arrow 222.

  Thereafter, the control circuit 67 reverses the recording direction of the PU 64 from the previous recording direction by the thread 66 via the thread drive circuit 76 (from the inner circumferential direction to the outer circumferential direction or from the outer circumferential direction to the inner circumferential direction) (S19).

  Then, the recording operation (S21) similar to step S9 is repeated until the CPU 61 determines that the recording is finished (YES in S23). When it is determined that the data recording is finished (YES in S23), a reset process is performed (S25). That is, the diffraction grating rotating actuator 13 sets the diffraction grating 12 to an initial state, for example, an angle at which a light spot is formed on the straight line L1 that is a position for the first layer 81.

  As described above, even when the recording operation is changed by changing the layer of the optical disk when performing the recording operation according to the DPP method, the sub beam spot with respect to the main beam spot MB formed on the optical disk 10 by rotating the diffraction grating 12 is rotated. By changing the arrangement of SB1 and SB2 to an arrangement corresponding to the recording direction, it is possible to prevent an offset from occurring in the signal DPP of the tracking error signal TE, thereby enabling preferable tracking control.

  Here, the change in the recording direction is assumed to occur with the change in the recording target layer, but the present invention is not limited to this. For example, even when the recording direction from the inner periphery to the outer periphery is changed from the outer periphery to the inner periphery in the same recording layer, the change in the recording direction is detected, and in response to the detection, FIG. The diffraction grating 12 may be rotated on the same principle to change the arrangement of the sub beam spots SB1 and SB2 with respect to the main beam spot MB imaged on the optical disc 10 to an arrangement corresponding to the recording direction.

  The embodiment disclosed this time should be considered as illustrative in all points and not restrictive. The scope of the present invention is defined by the terms of the claims, rather than the description above, and is intended to include any modifications within the scope and meaning equivalent to the terms of the claims.

1 is a block configuration diagram of an optical pickup according to an embodiment of the present invention. FIG. 1 is a block diagram of an optical disc recording / reproducing apparatus according to an embodiment of the present invention. It is a processing flowchart concerning an embodiment of this invention. It is a figure explaining the recording condition of the 1st layer concerning an embodiment of this invention. It is a figure explaining the various signals detected corresponding to FIG. It is a figure explaining the recording condition of the 2nd layer concerning an embodiment of this invention. It is a figure explaining the various signals detected corresponding to FIG. It is a figure explaining the procedure which calculates | requires the angle which concerns on embodiment of this invention. It is a figure explaining the opposite system in the conventional 2 layer DVD recording. It is a figure explaining the recording condition of the conventional 1st layer. It is a figure explaining the various signals detected corresponding to FIG. It is a figure explaining the recording condition of the conventional 2nd layer. It is a figure explaining the various signals detected corresponding to FIG. It is a figure explaining the light-receiving surface of a photodetector.

Explanation of symbols

  12 diffraction gratings, 13 diffraction grating rotation actuators, 68 rotation amount determination unit, 69 layer discrimination unit, 73 rotation actuator circuit, 81 first layer, 82 second layer.

Claims (6)

On the recording layer of the optical disk in which a plurality of tracks are formed concentrically, the light beam from the light source is irradiated by the diffraction grating portion into three light beams of the 0th order light beam and the ± 1st order light beam, and the main beam is emitted from the 0th order light beam. The beam spot is formed and two sub beam spots are formed by the ± first order light beam so as to sandwich the main beam spot, and the main beam spot is formed on the track to record data, and the diffraction The positional relationship of the respective gratings for the 0th-order light beam and the ± 1st-order light beam in the grating portion coincides with the positional relationship of the main beam spot and the two sub beam spots in the recording layer. A control device for an optical pickup obtained based on the amount of reflected light of the two sub beam spots,
The recording direction in the recording layer is either the first direction from the inner track to the outer track or the second direction from the outer track to the inner track, and one of the two sub beam spots is in the tracking direction. The other is formed in front of the main beam spot and the rear,
The optical pickup control device comprises:
A recording direction change detecting means for detecting that the recording direction has changed during data recording;
When the change in the recording direction is detected by the recording direction change detecting means, the diffraction grating portion is set at a predetermined angle so as to reverse the positions of the two sub beam spots with respect to the main beam spot before and after the change in the recording direction. A diffraction grating rotating means for rotating around the grating of the main beam spot,
The optical disc comprises a plurality of recording layers,
The change in the recording direction indicates that the recording layer to be recorded has changed from one recording layer to another recording layer,
The optical pickup control device comprises:
Address information indicating a recording position read from the track at the time of data recording is compared with address information corresponding to each of the plurality of recording layers, and a change in the recording layer to be recorded is determined based on the comparison result. Recording layer discriminating means to perform,
A rotation angle determination unit that determines the predetermined angle;
The sub-beam spot is formed in a region disposed between the tracks formed concentrically,
The optical pickup control device, wherein the predetermined angle is determined based on a distance between the main beam spot and the sub beam spot and a distance between two regions adjacent to the track. On the recording layer of the optical disk in which a plurality of tracks are formed concentrically, the light beam from the light source is irradiated by the diffraction grating portion into three light beams of the 0th order light beam and the ± 1st order light beam, and the main beam is emitted from the 0th order light beam. The beam spot is formed and two sub beam spots are formed by the ± first order light beam so as to sandwich the main beam spot, and the main beam spot is formed on the track to record data, and the diffraction The positional relationship of the respective gratings for the 0th-order light beam and the ± 1st-order light beam in the grating portion coincides with the positional relationship of the main beam spot and the two sub beam spots in the recording layer. A control device for an optical pickup obtained based on the amount of reflected light of the two sub beam spots,
The recording direction in the recording layer is either the first direction from the inner track to the outer track or the second direction from the outer track to the inner track, and one of the two sub beam spots is in the tracking direction. The other is formed in front of the main beam spot and the rear,
The optical pickup control device comprises:
A recording direction change detecting means for detecting that the recording direction has changed during data recording;
When the change in the recording direction is detected by the recording direction change detecting means, the diffraction grating portion is set at a predetermined angle so as to reverse the positions of the two sub beam spots with respect to the main beam spot before and after the change in the recording direction. An optical pickup control device comprising: a diffraction grating rotating unit that rotates about a grating of a main beam spot. The optical disc comprises a plurality of recording layers,
The optical pickup control device according to claim 2, wherein the change in the recording direction indicates that a recording layer to be recorded has changed from one recording layer to another recording layer.   Address information indicating a recording position read from the track at the time of data recording is compared with address information corresponding to each of the plurality of recording layers, and a change in the recording layer to be recorded is determined based on the comparison result. The optical pickup control device according to claim 3, further comprising a recording layer discriminating unit for performing the recording layer discrimination.   The optical pickup control device according to claim 2, further comprising a rotation angle determination unit that determines the predetermined angle. The sub-beam spot is formed in a region disposed between the tracks formed concentrically,
The said predetermined angle is determined based on the distance between the said main beam spot and a sub beam spot, and the distance between the two said area | regions adjacent to the said track | truck. Optical pickup control device.

Images