JP2007102831A - Optical pickup and optical disk device using it - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To make it possible to perform accurate phase difference adjustment by making irradiation positions of an optical disk with three branched optical beams into appropriate positions, and acquire a successful tracking error signal to an optical disk having a guidance groove. <P>SOLUTION: An optical pickup is provided with; a light source 31 of a predetermined wavelength; a light branch element 32 which branches an optical beam into three; an objective lens 33 which condenses three optical beams onto an optical disk 11; first to third photo detectors 41, 42 and 43 which receive three reflected return optical beams, respectively; and a signal processing circuit section 45 for outputting the signal of the first-third photo detectors to the outside. Each of the first to third photo detectors has quadrant light receiving areas. The signal processing circuit section 45 has first to fourth output signal lines connected and through which the signals acquired from a predetermined light receiving area are outputted outside. The signal processing circuit section 45 has a switching means which is controlled by a control section and switches a signal connected to each of output signal lines to the signal which can be acquired from the predetermined light receiving area. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to an optical pickup that performs recording and / or reproduction on an information recording medium such as an optical disk and an optical disk apparatus using the same.

  Conventionally, in an optical pickup and an optical disc apparatus, various methods are used to generate a tracking error signal and a focusing error signal.

  In order to generate a good tracking error signal and focusing error signal for a recording / reproducing optical disc such as a DVD-RAM having a guide groove for tracking servo, it is described in, for example, JP-A-2003-178482. An optical pickup including a photodetector having a light receiving region divided into twelve parts, such as an optical pickup, is known. (See Patent Document 1).

  The optical pickup disclosed in Japanese Patent Laid-Open No. 2003-178482 irradiates a predetermined position of an optical disc with three light beams separated by a diffraction grating, and the returned light beam is detected by a 12-divided photodetector having a predetermined configuration. It is receiving light. This optical pickup can greatly reduce the influence of disturbance by generating a good focusing error signal by the astigmatism method, and it generates a good tracking error signal by the push-pull method. Thus, the effect of offset generated can be greatly reduced.

  However, in such an optical pickup, the phase difference is adjusted by adjusting the phase adjustment of the three light beams so that the side push-pull is maximized for the convenience of signal processing. It wasn't. For this reason, it has been difficult to accurately obtain a good tracking error signal.

JP 2003-178482 A

  An object of the present invention is to enable accurate phase difference adjustment by appropriately irradiating a recording track of an optical disc with three light beams branched by an optical branching element, and continuously on a signal recording surface. It is an object of the present invention to provide an optical pickup capable of obtaining a good tracking error signal for an optical disc provided with the guide groove and an optical disc apparatus using the same.

  In order to achieve this object, an optical pickup according to the present invention includes a light source that emits a light beam having a predetermined wavelength, a light branching element that branches the light beam emitted from the light source into three light beams, An objective lens that condenses the branched three light beams on the signal recording surface of the optical disc, and a first light detection that receives the main beam among the three return light beams reflected by the signal recording surface. And the remaining first and second sub-beams of the three return light beams that are provided on both sides in the tangential direction of the recording track of the optical disc of the first photodetector and reflected by the signal recording surface. Each of the second and third photodetectors for receiving light, and a signal processing circuit unit for outputting the signals obtained by the first to third photodetectors to the outside, the first photodetector , Divided into two in the tangential direction, the tangent The first and second light receiving areas arranged on the second photodetector side and the second arranged on the third photodetector side are divided into four by being divided into two in the direction orthogonal to the direction. The second photodetector is divided into two in the tangential direction, and is divided into four by dividing into two in the direction orthogonal to the tangential direction. A third light detection unit including fifth and sixth light receiving regions disposed on the side opposite to the photodetector side and seventh and eighth light receiving regions disposed on the first photodetector side; The device is divided into two in the tangential direction, and is divided into four by being divided into two in the direction perpendicular to the tangential direction, and the ninth and tenth light receiving regions disposed on the first photodetector side, and In the optical pickup having the eleventh and twelfth light receiving regions arranged on the opposite side to the first photodetector side, the signal processing circuit unit The fifth light receiving region of the second light detector and the third light detector disposed on the same side as the first light receiving region of the first light detector and the tangential direction. A first output signal line to which a signal obtained from the ninth light receiving region is connected and output to the outside is arranged on the same side as the second light receiving region of the first photodetector and the tangential direction. A second output signal line to which signals obtained from the sixth light receiving region of the second photodetector and the tenth light receiving region of the third photodetector are connected and output to the outside; and The seventh light receiving region of the second photodetector and the eleventh of the third photodetector arranged on the same side as the second light receiving region of the first photodetector with respect to the tangential direction. A third output signal line to which a signal obtained from the light receiving region is connected and output to the outside, and a first light receiving of the first photodetector And signals obtained from the eighth light receiving region of the second photodetector and the twelfth light receiving region of the third photodetector arranged on the same side as the region and the tangential direction are connected. A fourth output signal line that outputs to the outside, and the signal processing circuit unit is controlled by the control unit to transmit a signal connected to the first output signal line of the second photodetector. Switch to signals obtained from the fifth and sixth light receiving areas, and switch signals connected to the second output signal lines to signals obtained from the ninth and tenth light receiving areas of the third photodetector. The signal connected to the third output signal line is switched to the signal obtained from the seventh and eighth light receiving areas of the second photodetector, and the signal connected to the fourth output signal line is changed. Switching to signals obtained from the 11th and 12th light receiving areas of the third photodetector A switching means.

  In order to achieve the above object, an optical disc apparatus according to the present invention is an optical disc apparatus including an optical pickup that records and / or reproduces information on an optical disc, and a disc rotation driving unit that rotates the optical disc. As the optical pickup used in this optical disc apparatus, the one described above is used.

  An optical pickup according to the present invention and an optical disk apparatus using the optical pickup perform accurate phase difference adjustment by appropriately irradiating the recording track of the optical disk with the three light beams branched by the optical branching element. And a good tracking error signal can be obtained for an optical disc provided with a continuous guide groove on the signal recording surface.

  Hereinafter, an optical disk apparatus using an optical pickup to which the present invention is applied will be described with reference to the drawings.

  The optical disc apparatus 10 is a recording / reproducing apparatus capable of recording and / or reproducing information signals with respect to the optical disc 11. The optical disk 11 used here has, for example, a guide groove (groove) for tracking error signals, and a land / groove system in which information can be rewritten in both a land (between guide grooves) and a groove (guide groove). DVD-RAM.

  As shown in FIG. 1, the optical disk apparatus 10 includes a spindle motor 12 as a driving means for rotating the optical disk 11, a motor control circuit 13 for controlling the spindle motor 12, and an optical beam applied to the optical disk 11 rotated by the spindle motor 12. Pickup 1 that detects the return light beam reflected by the optical disk 11, the RF amplifier 15 that amplifies the electrical signal output from the optical pickup 1, and the focusing servo signal and tracking servo signal of the objective lens are generated. A servo circuit 16 and a subcode extraction circuit 17 for extracting subcode data are provided.

  The optical disk apparatus 10 is connected to a host device such as a personal computer as a recording system, and has an input terminal 18 to which data to be recorded is input, and an error correction code for the recording data input to the input terminal 18. An error correction encoding circuit 19 that performs the encoding process, a modulation circuit 20 that modulates the data that has been subjected to the error correction encoding process, and a recording processing circuit 21 that performs the recording process on the modulated recording data.

  Further, the optical disc apparatus 10 includes, as a reproduction system, a demodulation circuit 22 that demodulates reproduction data read from the optical disc 11, an error correction decoding circuit 23 that performs error correction decoding processing on the demodulated reproduction data, And an output terminal 24 for outputting data subjected to error correction decoding processing. Furthermore, the optical disc apparatus 10 includes an operation unit 25 that inputs operation signals to the apparatus, a memory 26 that stores various control data and the like, and a control circuit 27 that controls the overall operation.

  The spindle motor 12 is provided with a disk table on which the optical disk 11 is mounted on the spindle, and rotates the optical disk 11 mounted on the disk table. The motor control circuit 13 drives and controls the spindle motor 12 so that the optical disk can be rotated by CLV (Constant Linear Velocity). Specifically, the motor control circuit 13 drives and controls the spindle motor 12 so that the rotational speed of the optical disk 11 is constant based on the reference clock from the crystal oscillator and the clock from the PLL circuit. Note that the optical disk 11 may be rotated by control combining CAV (Cnstant Angular Velocity) or CLV and CAV.

  The optical pickup 1 includes a light source such as a semiconductor laser that emits a light beam having a predetermined wavelength, an objective lens that focuses the light beam emitted from the light source, and a photodetector that detects a return light beam reflected by the optical disk 11. Etc. When reading data recorded on the optical disk 11, the optical pickup 1 sets the output of the semiconductor laser to a standard level and emits a light beam, which is laser light, from the semiconductor laser. Further, when the recording data is recorded on the optical disc 11, the optical pickup 1 sets the output of the semiconductor laser to a recording level higher than the standard level at the time of reproduction, and emits a light beam that is laser light from the semiconductor laser. The optical pickup 1 irradiates the optical disk 11 with a light beam at the time of recording / reproduction, detects the returned light beam reflected by the signal recording surface with a photodetector, and performs photoelectric conversion. The objective lens is held by an objective lens driving mechanism such as a biaxial actuator, and is driven and displaced in the focusing direction parallel to the optical axis of the objective lens based on the focusing servo signal. The objective lens is also based on the tracking servo signal. Is driven and displaced in a tracking direction orthogonal to the optical axis. The configuration of the optical system such as the semiconductor laser, the objective lens, and the photodetector will be described in detail later.

  The RF amplifier 15 generates an RF signal, a focusing error signal, and a tracking error signal based on an electrical signal from a photodetector that constitutes the optical pickup 1. The focusing error signal and the tracking error signal are generated as described later. The RF amplifier 15 outputs an RF signal to the demodulation circuit 22 and outputs a focusing error signal and a tracking error signal to the servo circuit 16 during reproduction.

  The servo circuit 16 generates a servo signal for reproducing the optical disc 11. Specifically, the servo circuit 16 generates a focusing servo signal based on the focusing error signal input from the RF amplifier 15 so that the focusing error signal becomes zero, and the tracking signal input from the RF amplifier 15. Based on the error signal, a tracking servo signal is generated so that the tracking error signal becomes zero. The servo circuit 16 outputs the focusing servo signal and the tracking servo signal to the drive circuit of the objective lens drive mechanism that constitutes the optical pickup 1. The drive circuit drives the biaxial actuator based on the focusing servo signal, drives and displaces the objective lens in a focusing direction parallel to the optical axis of the objective lens, drives the biaxial actuator based on the tracking servo signal, and drives the objective lens. The objective lens is driven and displaced in a tracking direction orthogonal to the optical axis.

  The subcode extraction circuit 17 extracts subcode data from the RF signal output from the RF amplifier 15 and outputs the extracted subcode data to the control circuit 27 so that the control circuit 27 can specify address data and the like. .

  The input terminal 18 serves as an interface such as a small computer system interface (SCSI), an advanced technology attachment packet interface (ATAPI), a universal serial bus (USB), or an IEEE (Institute of Electrical and Electronic Engineers) 1394 of a host device such as a personal computer. Recording data such as audio data, movie data, a computer program, and processing data processed by a computer is input from the host device, and the input recording data is output to the error correction encoding circuit 19.

  The error correction encoding circuit 19 performs error correction encoding processing such as cross interleave Reed-solomon code (CIRC) and Reed-Solomon product encoding, and performs error correction encoding processing, for example. Recording data is output to the modulation circuit 20. The modulation circuit 20 has a conversion table such as 8-14 modulation, 8-16 modulation, etc., converts input 8-bit recording data into 14 bits or 16 bits, and outputs the converted data to the recording processing circuit 21. . The recording processing circuit 21 performs processing such as NRZ (Non Return to Zero) and NRZI (Non Return to Zero Inverted) on the recording data input from the modulation circuit 20 and recording compensation processing, and outputs the processed data to the optical pickup 1. .

  The demodulation circuit 22 has a conversion table similar to that of the modulation circuit 20, converts the RF signal input from the RF amplifier 15 from 14 bits or 16 bits to 8 bits, and converts the converted 8-bit reproduction data into an error. The data is output to the correction decoding circuit 23. The error correction decoding circuit 23 performs error correction decoding processing on the data input from the demodulation circuit 22 and outputs it to the output terminal 24. The output terminal 24 is electrically connected to the interface of the host device described above. The reproduction data output from the output terminal 24 is displayed on a monitor connected to the host device, and converted into reproduction sound by a speaker and output.

  The operation unit 25 generates various operation signals for operating the optical disc apparatus 10 and outputs the generated various operation signals to the control circuit 27. Specifically, the operation unit 25 is recorded on the recording button 25b for starting recording of recording data on the optical disc 11 mounted on the disc table and the optical disc 11 in addition to the eject button 25a provided in the optical disc apparatus 10. A playback button 25c for starting playback of the data being recorded and a stop button 25d for stopping the recording / playback operation. The recording button 25b, the playback button 25c, the stop button 25d, and the like are not necessarily provided on the optical disc apparatus 10 together with the eject button 25a. For example, by operating the keyboard, mouse, etc. of the host device, an interface is provided from the host device. A recording start signal, a reproduction start signal, a stop signal, and the like may be input to the control circuit 27 via the control circuit 27.

  The memory 26 is a memory such as an EP-ROM (Erasable Programmable Read-Only Memory), and stores various control data and programs executed by the control circuit 27. Specifically, in the memory 26, various control data corresponding to the type of the optical disk 11 of the thread motor 28 which is a driving source when the optical pickup 1 is fed in the radial direction of the optical disk 11 mounted on the disk table. Stored.

  The control circuit 27 is composed of a microcomputer, a CPU, and the like, and controls the operation of the entire apparatus according to an operation signal from the operation unit 25. In addition, the control circuit 27 detects a different format from the surface reflectance of the optical disk 11, a difference in shape and shape, and the like to determine the type of the optical disk 11, and the optical pickup 1 according to the detected type of the optical disk 11. The light source and output power of the semiconductor laser are switched.

  The optical disc apparatus 10 configured as described above rotates the optical disc 11 by the spindle motor 12 and drives and controls the sled motor 28 in accordance with the control signal from the servo circuit 16 so that the optical pickup 1 can be used as desired on the optical disc 11. By moving to a position corresponding to the recording track, information is recorded on and reproduced from the optical disc 11.

  Next, the above-described optical pickup 1 to which the present invention is applied will be described.

  As shown in FIG. 2, the optical pickup 1 to which the present invention is applied includes a light source 31 that emits a light beam having a predetermined wavelength, and a light beam emitted from the light source 31 from a main beam and first and second sub beams. A diffraction grating 32 as an optical branching element for branching into three light beams, an objective lens 33 for condensing the three light beams branched into the diffraction grating 32 on the signal recording surface of the optical disk 11, Of the three return light beams reflected on the signal recording surface, the first photodetector 41 that receives the main beam, and on the first of the three return light beams reflected on the signal recording surface of the optical disc 11. A second photodetector 42 that receives one sub-beam, a third photodetector 43 that receives the second sub-beam of the three return light beams reflected by the signal recording surface of the optical disc 11, and this 1 and a signal processing circuit section 45 for outputting a signal obtained by the third photodetector 41, 42 and 43 to the outside.

  The optical pickup 1 is provided between the objective lens 33 and the diffraction grating 32, and is emitted from the light source 31 by changing the optical path of the return (return path side) light beam reflected by the signal recording surface of the optical disc 11. A collimator lens that is provided between the beam splitter 34 that separates from the optical path of the outgoing light beam, and between the objective lens 33 and the beam splitter 34 and changes the divergence angle of the light beam emitted from the light source 31 to produce parallel light. 35, a rising mirror 36 that is provided between the objective lens 33 and the collimator lens 35 and reflects the light beam parallel to the collimator lens 35 to the optical disc 11 side, a beam splitter 34, and first to third. The three returned light beams reflected by the beam splitter 34 are provided between the first and second photodetectors 41, 42, and 43, respectively. And a cylindrical lens 37 for condensing the photodetector 41, 42 and 43.

  The light source 31 is a semiconductor laser that emits a laser beam having a wavelength of about 650 nm, for example. The diffraction grating 32 includes zero-order light (hereinafter referred to as “main beam”) that directly transmits the light beam emitted from the light source 31 and ± first-order diffracted light (hereinafter referred to as “main beam”) that is branched from the main beam at a predetermined diffraction angle. Branches into “first sub-beam” and “second sub-beam”, respectively.

  The beam splitter 34 transmits the main beam branched by the diffraction grating 32 and the first and second sub beams (hereinafter, referred to as “three light beams”) to be emitted to the collimator lens 35 side, and for signal recording. The three returned light beams reflected by the surface are reflected and emitted to the cylindrical lens 37 side.

  The collimator lens 35 converts the three light beams incident through the beam splitter 34 into parallel light and emits them to the rising mirror 36 side. The raising mirror 36 reflects and emits the three light beams that have been collimated by the collimator lens 35 to the objective lens 33 side.

  The objective lens 33 condenses the three light beams reflected by the rising mirror 36 on the signal recording surface of the optical disc 11, and the main spot 100 and the first and second sub-spots 101 and 102 (hereinafter referred to as “3”). Individual light spots "). The three light beams collected on the signal recording surface of the optical disc 11 are reflected by the signal recording surface, and are reflected by the beam splitter 34 described above via the same optical path as that of the forward light, and the cylindrical lens 37. Is incident on.

  The irradiation position interval in the optical disk radial direction of the three light spots diffracted and branched by the diffraction grating 32 and collected by the objective lens 33 is set so as to coincide with approximately half of the guide groove pitch of the optical disk 11. That is, for example, when the main spot 100 is located in the middle of the guide groove (land) of the optical disc 11, the first and second sub-spots 101 and 102 are adjacent to the guide groove (groove). ) To be located in the middle. When the irradiation positions of the three light spots are shifted relative to the guide groove, the irradiation position interval in the optical disc radial direction of the three light spots is always maintained, while the signal recording is performed. The returning light beam on the surface has a characteristic intensity distribution pattern that changes periodically under the influence of diffraction by the guide groove. When the intensity distribution patterns of the returning light beam of the main spot 100 and the returning light beams of the first and second sub-spots 101 and 102 are compared, there is a change that is reversed left and right.

  The cylindrical lens 37 gives a predetermined astigmatism for detecting a focusing error signal to be described later to the passing light beam.

  As shown in FIG. 3, in the first to third photodetectors 41, 42, and 43, the intensity centers of the three light spots are the centers of the light receiving regions of the respective photodetectors, that is, described later. It is arranged so as to coincide with the intersection of the dividing lines. The second and third photodetectors 42 and 43 are provided on both sides in the tangential direction of the recording track of the optical disc 11 of the first photodetector 41.

  As shown in FIG. 3, the first photodetector 41 is divided into two in the tangential direction of the recording track of the optical disc 11 and divided into two in the direction perpendicular to the tangential direction, so that the first photodetector 41 is divided into four in a so-called square shape. The first and second light receiving areas 51 and 52 arranged on the second photodetector side, and the third and fourth light receiving areas 53 and 54 arranged on the third photodetector side, have. Here, the third light receiving region 53 is arranged side by side with the second light receiving region 52, that is, on the same side with respect to the tangential direction. The fourth light receiving region 54 is arranged side by side with the first light receiving region 51, that is, on the same side with respect to the tangential direction.

  Further, as shown in FIG. 3, the second photodetector 42 is divided into two in the tangential direction and into two in the direction perpendicular to the tangential direction, so that the second photodetector 42 is divided into four in a so-called square shape. The fifth and sixth light receiving regions 55 and 56 disposed on the opposite side of the first photodetector side, and the seventh and eighth light receiving regions 57 and 58 disposed on the first photodetector side. Have. Here, the fifth and eighth light receiving regions 55 and 58 are arranged side by side with the first light receiving region 51, that is, on the same side with respect to the tangential direction. The sixth and seventh light receiving regions 56 and 57 are arranged side by side with the second light receiving region 52, that is, on the same side with respect to the tangential direction.

  As shown in FIG. 3, the third photodetector 43 is divided into two in the tangential direction and divided into two in a direction orthogonal to the tangential direction, so that the third photodetector 43 is divided into four so-called rice fields. Ninth and tenth light receiving regions 59 and 60 disposed on the photodetector side, and eleventh and twelfth light receiving regions 61 and 62 disposed on the opposite side to the first photodetector side. ing. Here, the ninth and twelfth light receiving regions 59 and 62 are arranged side by side with the first light receiving region 51, that is, on the same side with respect to the tangential direction. The tenth and eleventh light receiving regions 60 and 61 are arranged side by side with the second light receiving region 52, that is, on the same side with respect to the tangential direction.

  Each detection current detected by photoelectric conversion in the first to twelfth light receiving regions 51 to 62 of the first to third photodetectors 41, 42, and 43 is a package of the first to third photodetectors. The voltage is converted into a voltage by a current-voltage conversion amplifier provided inside and sent to the signal processing circuit unit 45.

  As shown in FIGS. 4 to 7, the signal processing circuit unit 45 performs the first to sixth states for performing gain adjustment in the tracking servo state and the focusing servo state, and three light spots before factory shipment. Changeover switches 63, 64, 65, and 66 are provided as switching means for switching the seventh state, which is an adjustment state in which the position is adjusted to adjust the phase difference of the three light beams. Further, the signal processing circuit unit 45 switches the gain at the time of recording and reproduction, specifically, a change-over switch 75 for switching between the first state and the fifth state, and between the second state and the sixth state. , 76, 77, 78 are provided.

  As shown in Table 1 and FIG. 4, the changeover switch 63 has switch units 63a, 63b, 63c, 63d, and 63e. When the mode is 1 or 5 (MODE-1 / 5), the switch unit 63a is on. Then, the other switch units are turned off, and the calculation unit 67a calculates the first state or the fifth state. In mode 2 or 6 (MODE-2 / 6), the switch unit 63b is turned on, the other switch units are turned off, and the calculation unit 67b is set to the second state or the sixth state. Calculated. In mode 3 (MODE-3), the switch unit 63c is turned on, the other switch units are turned off, and the computation unit 67c performs computation so as to enter the third state. In mode 4 (MODE-4), the switch unit 63d is turned on, the other switch units are turned off, and the computation unit 67d performs computation so as to enter the fourth state. Further, in the adjustment mode (ADJUST), which is an adjustment before factory shipment, the switch unit 63e is turned on, the other switch units are turned off, and the computation unit 67e performs computation so as to enter the seventh state. However, at the time of this adjustment (adjustment mode), as will be described later, the combination of signals output to the outside is different from that in other states. In the adjustment mode, the gain is substantially the same as in mode 1. In modes 1 and 2, the changeover switch 75 is turned off, and in other cases, the changeover switch 75 is turned on to switch the first to seventh states. L gain for reproduction, H gain for reproduction, L gain for recording, M1 gain for recording, M2 gain for recording, H gain for recording, and gain for adjustment Gain can be selected.

  As shown in Table 1 and FIGS. 5 to 7, the changeover switches 64, 65, 66 are respectively switch parts 64 a, 64 b, 64 c, 64 d, 64 e, switch parts 65 a, 65 b, 65 c, 65 d, 65 e, switch part 66a, 66b, 66c, 66d, 66e, and each switch section is turned on / off in the mode 1 to 6 or the adjustment mode (during adjustment before shipment from the factory) as in the case of the selector switch 63. At the same time, the changeover switches 76, 77, 78 are turned on / off, and are calculated by the respective calculation units 68a to 68e, calculation units 69a to 69e, and calculation units 70a to 70e to be in the first to seventh states. The

  The signal processing circuit unit 45 is obtained from the fifth and ninth light receiving areas 55 and 59 when the first to sixth states are set by the changeover switches 63, 64, 65, and 66 described above. A first output signal line 71 to which a signal to be output is connected and output to the outside, and a second output signal line 72 to which a signal obtained from the sixth and tenth light receiving regions 56 and 60 is connected and output to the outside The third output signal line 73 to which the signals obtained from the seventh and eleventh light receiving regions 57 and 61 are connected and output to the outside is connected to the signal obtained from the eighth and twelfth light receiving regions 58 and 62. The fourth output signal line 74 to be output to the outside and the fifth to eighth output signal lines (not shown) from which the signals obtained from the first to fourth light receiving areas 51 to 54 are output to the outside as they are, respectively. Have.

  Hereinafter, the signal output from the first output signal line 71 is (e + i), which is the sum of the signal e obtained from the fifth light receiving region 55 and the signal i obtained from the ninth light receiving region 59, and The signal output from the second output signal line 72 is (f + j) which is the sum of the signal f obtained from the sixth light receiving region 56 and the signal j obtained from the tenth light receiving region 60, and the third output. The signal output from the signal line 73 is defined as the sum (g + k) of the signal g obtained from the seventh light receiving region 57 and the signal k obtained from the eleventh light receiving region 61, and the fourth output signal line 74. Is described as (h + 1), which is the sum of the signal h obtained from the eighth light receiving region 58 and the signal l obtained from the twelfth light receiving region 62. Further, the signal output from the fifth output signal line is the signal a obtained from the first light receiving region 51, and the signal output from the sixth output signal line is obtained from the second light receiving region 52. A signal b, a signal output from the seventh output signal line, is a signal c obtained from the third light receiving region 53, and a signal output from the eighth output signal line is output from the fourth light receiving region 54. This will be described as the signal d obtained.

  The signal processing circuit unit 45 is a combination of signals output to the outside from each of the first to eighth output signal lines by switching the first state to the sixth state by the changeover switches 63, 64, 65, and 66. Is not changed, but the gain of the signal is changed and output to the outside.

  Then, when the signal processing circuit unit 45 is switched to the seventh state by the change-over switches 63, 64, 65, and 66, the signal connected to the first output signal line 71 is supplied to the fifth and sixth signals. Switching to the signal (e + f) obtained from the light receiving areas 55 and 56, and switching the signal connected to the second output signal line 72 to the signal (i + j) obtained from the ninth and tenth light receiving areas 59 and 60, The signal connected to the third output signal line 73 is switched to the signal (g + h) obtained from the seventh and eighth light receiving regions 57 and 58, and the signal connected to the fourth output signal line 74 is changed to the eleventh and eighth signals. The signal is switched to the signal (k + l) obtained from the twelfth light receiving areas 61 and 62.

  Next, the tracking error signal and the focusing error signal generated in the optical pickup 1 described above will be described.

  The tracking error signal is switched by the selector switches 63, 64, 65, 66 so that the signal processing circuit unit 45 is in any one of the first to sixth states, and the first and second output signals are switched. The sum of signals output from the lines 71 and 72, the sum of signals output from the third and fourth output signal lines 73 and 74, and the first to fourth light receiving regions of the first photodetector 41. And signals output from the fifth to eighth output signal lines obtained from 51 to 54.

  That is, first, signals (a + b) − (c + d) are output from the signals a, b, c, and d output from the fifth to eighth output signal lines by an adder and subtracter (not shown). This signal (a + b) − (c + d) corresponds to the detected light quantity of each region when the main spot 100 on the signal recording surface of the optical disc 11 is divided into two in the tracking direction (radial direction) of the optical disc 11. The difference signal of the individual signals corresponds to a tracking error signal of the main spot 100 on the signal recording surface of the optical disc 11 detected by a so-called push-pull method.

  On the other hand, from the signals (e + i), (f + j), (g + k), and (h + l) output from the first to fourth output signals, (e + i + f + j) and (g + k + h + l) are obtained by an adder (not shown). Further, {(e + i + f + j) − (g + k + h + l)} is obtained by a subtracter (not shown). Further, the signal is amplified and output at a predetermined amplification factor K1.

  Finally, an output signal {(a + b) − (c + d)} − K1 × {(e + i + f + j) − (g + k + h + l)} obtained by subtracting the above signal is obtained as a tracking error signal by the subtractor. This signal is obtained from the tracking error signal of the main spot 100 obtained from the first photodetector 41, and the first and second sub-spots 101, 101 obtained from the second and third photodetectors 42, 43. This is a signal obtained by subtracting the tracking error signal 102.

  The tracking error signal obtained in this manner is a good signal in which the influence of offset due to the displacement of the objective lens, which was a drawback of the push-pull method, is greatly eliminated despite the push-pull method.

  The focusing error signal is switched so that the signal processing circuit unit is in any one of the first to sixth states by the changeover switches 63, 64, 65, 66, and the first and third output signal lines 71 are switched. , 73, the sum of the signals output from the second and fourth output signal lines 72, 74, and the first to fourth light receiving regions 51-54 of the first photodetector 41. Are generated from the signals output from the fifth to eighth output signal lines.

  That is, first, signals (a + c) − (b + d) are output from the signals a, b, c, and d output from the fifth to eighth output signal lines by an adder and subtracter (not shown). This signal (a + c) − (b + d) corresponds to a defocus signal of the main spot 100 on the signal recording surface of the optical disc 11 detected by a so-called astigmatism method.

  On the other hand, from the signals (e + i), (f + j), (g + k), and (h + l) output from the first to fourth output signals, (e + i + g + k) and (f + j + h + l) are obtained by an adder (not shown). Further, {(e + i + g + k) − (f + j + h + l)} is obtained by a subtracter (not shown). Further, the signal is amplified and output at a predetermined amplification factor K2.

  Finally, the adder obtains an output signal {(a + c) − (b + d)} + K2 {(e + i + g + k) − (f + j + h + l)} obtained by adding the above signals as a focusing error signal. This signal includes the defocus signal of the main spot 100 obtained from the first photodetector 41 and the first and second sub-spots 101, obtained from the second and third photodetectors 42, 43. It corresponds to a signal obtained by adding the sum signal of the defocus signals of 102 in a state where the signal amplitudes are combined.

  The focusing error signal obtained in this way is a good signal in which the disturbance of the defocus signal due to diffraction in the guide groove is largely eliminated.

  As described above, the optical pickup 1 is a push-pull type by using the first to third photodetectors 41, 42, and 43 divided into four parts and the signal processing circuit unit 45 having a predetermined configuration. Regardless of the push-pull method, the good tracking error signal, which largely offsets the effect of offset due to the displacement of the objective lens, and the excellent defocusing signal disturbance due to diffraction in the guide groove, are eliminated. A focusing error signal can be obtained.

  Next, the adjustment of the phase difference of the three light spots by adjusting the irradiation position of the three light beams on the recording track of the optical disk 11 in the optical pickup 1 described above will be described.

  The detection signal for adjusting the phase difference is switched to the seventh state by the change-over switches 63, 64, 65, 66, that is, the adjustment state is changed to the first and third output signal lines. From the sum of the signals output from 71 and 73 and the sum of the signals output from the second and fourth output signal lines 72 and 74, the signal recording surface of the optical disc 11 of the first and second sub beams is obtained. Adjust the phase difference.

  That is, from the signals (e + f), (i + j), (g + h), (k + l) output from the first to fourth output signals, (e + f + g + h), (i + j + k + l) are obtained by an adder (not shown). Based on the signal, the irradiation position of the three light beams onto the recording track of the optical disk 11 can be adjusted to an appropriate position, and the phase difference of the three light spots can be adjusted. Here, the adjustment of the irradiation position of the three light beams onto the recording track of the optical disk 11 is performed by, for example, adjusting the diffraction grating 32 around the optical axis while viewing the Lissajous waveform of each spot by an adjusting device provided outside. This is done by rotating it.

  Thus, the sum of the signals output from the first and third output signal lines 71 and 73 and the second and fourth output signals that are switched to the adjustment state by the changeover switches 63, 64, 65, and 66. By adjusting the phase difference of the three light spots from the sum of the signals output from the lines 72 and 74, an accurate phase difference adjustment can be performed. By making the irradiation position of the second sub-spots 101 and 102 accurate, an accurate tracking error signal can be obtained.

  That is, when the switching means is not provided, the phase difference adjustment has only to be adjusted so that the side push-pull is maximized. More specifically, the adjustment was made so that {(e + i + f + j)-(g + k + h + l)} was maximized, and the difference was confirmed by the DPP level disc outer periphery difference.

  In contrast, in the optical pickup 1 to which the present invention is applied, as described above, the phase difference between the first sub-spot (e + f + g + h) that is the preceding spot and the second sub-spot (i + j + k + l) that is the subsequent spot. In other words, the phase difference between the preceding spot and the following spot can be confirmed directly, and an accurate phase difference adjustment can be performed. With an accurate phase difference adjustment, an accurate tracking error signal can be obtained. Obtainable.

  As described above, the optical pickup 1 to which the present invention is applied performs accurate phase difference adjustment with the irradiation position of the three light beams branched by the optical branching element on the recording track of the optical disk 11 being an appropriate position. This makes it possible to obtain a good tracking error signal for an optical disc provided with a continuous guide groove on the signal recording surface.

  Furthermore, the optical pickup 1 to which the present invention is applied enables an accurate phase difference adjustment of the three light beams, and is a push-pull method for an optical disc provided with a guide groove. A good tracking error signal that greatly eliminates the influence of offset due to the displacement of the objective lens, which was a drawback of the push-pull method, and a good focusing error signal that greatly eliminates the disturbance of the defocus signal due to diffraction in the guide groove And you can get

  Further, the optical disc apparatus 10 to which the present invention is applied can accurately adjust the phase difference by setting the irradiation position of the three light beams branched by the optical branching element to the recording track of the optical disc 11 at an appropriate position. In addition, since a good tracking error signal and focusing error signal can be obtained, information can be recorded / reproduced with respect to the optical disk 11 in a good manner.

It is a block circuit diagram which shows the structure of the recording / reproducing apparatus to which this invention is applied. It is an optical path diagram showing an example of an optical system of an optical pickup to which the present invention is applied. It is a top view which shows the structure of the 1st thru | or 3rd photodetector which comprises the optical pick-up to which this invention is applied. It is a figure which shows a part of structure of the signal processing circuit part which comprises the optical pick-up to which this invention is applied. It is a figure which shows a part of structure of the signal processing circuit part which comprises the optical pick-up to which this invention is applied. It is a figure which shows a part of structure of the signal processing circuit part which comprises the optical pick-up to which this invention is applied. It is a figure which shows a part of structure of the signal processing circuit part which comprises the optical pick-up to which this invention is applied.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 Optical pickup, 10 Recording / reproducing apparatus, 11 Optical disk, 12 Spindle motor, 27 Control part, 31 Light source, 32 Diffraction grating, 33 Objective lens, 34 Beam splitter, 35 Collimator lens, 36 Rising mirror, 37 Cylindrical lens, 41 1st 1 Photodetector, 42 Second Photodetector, 43 Third Photodetector, 45 Signal Processing Circuit Unit

Claims (3)

A light source that emits a light beam of a predetermined wavelength;
A light branching element for branching the light beam emitted from the light source into three light beams;
An objective lens for condensing the three branched light beams on the signal recording surface of the optical disc;
A first photodetector for receiving a main beam among the three return light beams reflected by the signal recording surface;
The remaining first and second sub-beams of the three return light beams, which are provided on both sides in the tangential direction of the recording track of the optical disk of the first photodetector, are respectively received by the signal recording surface. Second and third photodetectors;
A signal processing circuit unit for outputting signals obtained by the first to third photodetectors to the outside,
The first photodetector is divided into two in the tangential direction, and is divided into four by being divided in two in a direction orthogonal to the tangential direction, and is arranged on the second photodetector side. Two light receiving areas, and third and fourth light receiving areas arranged on the third photodetector side,
The second photodetector is divided into two in the tangential direction and divided into four by being divided into two in the direction perpendicular to the tangential direction, and is arranged on the opposite side to the first photodetector side. 5 and sixth light receiving areas, and seventh and eighth light receiving areas arranged on the first photodetector side,
The third photodetector is divided into two in the tangential direction, and is divided into four by being divided into two in the direction orthogonal to the tangential direction, and is arranged on the first photodetector side. In an optical pickup having 10 light-receiving regions and eleventh and twelfth light-receiving regions arranged on the side opposite to the first photodetector side,
The signal processing circuit unit includes a fifth light receiving region of the second photodetector and the fifth light receiving region arranged on the same side as the first light receiving region of the first photodetector with respect to the tangential direction. A first output signal line to which a signal obtained from the ninth light receiving region of the three photodetectors is connected and output to the outside;
The sixth light receiving region of the second photodetector and the third light detector of the third photodetector disposed on the same side as the second light receiving region of the first photodetector and the tangential direction. A second output signal line to which signals obtained from 10 light receiving regions are connected and output to the outside;
The seventh light receiving region of the second photodetector and the third light detector of the third photodetector disposed on the same side as the second light receiving region of the first photodetector with respect to the tangential direction. A third output signal line to which signals obtained from 11 light receiving areas are connected and output to the outside;
The eighth light receiving region of the second photodetector and the third light detector of the third photodetector arranged on the same side as the first light receiving region of the first photodetector with respect to the tangential direction. A fourth output signal line to which signals obtained from the 12 light receiving areas are connected and output to the outside;
The signal processing circuit unit is controlled by the control unit to switch a signal connected to the first output signal line to a signal obtained from the fifth and sixth light receiving regions of the second photodetector, The signal connected to the second output signal line is switched to a signal obtained from the ninth and tenth light receiving regions of the third photodetector, and the signal connected to the third output signal line is changed to the signal The signals obtained from the seventh and eighth light receiving regions of the second photodetector are switched, and the signal connected to the fourth output signal line is changed to the eleventh and twelfth light receiving of the third photodetector. An optical pickup having switching means for switching to a signal obtained from a region.   The sum of signals output from the first and third output signal lines switched by the switching unit and the signal output from the second and fourth output signal lines switched by the switching unit The optical pickup according to claim 1, wherein the irradiation position of the first and second sub beams to the recording track of the optical disc is adjusted based on the sum of the two. In an optical disc apparatus comprising an optical pickup for recording and / or reproducing information with respect to an optical disc having a guide groove, and a disc rotation driving means for rotating the optical disc.
The optical pickup includes a light source that emits a light beam having a predetermined wavelength,
A light branching element for branching the light beam emitted from the light source into three light beams;
An objective lens for condensing the three branched light beams on the signal recording surface of the optical disc;
A first photodetector for receiving a main beam among the three return light beams reflected by the signal recording surface;
The remaining first and second sub-beams of the three return light beams, which are provided on both sides in the tangential direction of the recording track of the optical disk of the first photodetector, are respectively received by the signal recording surface. Second and third photodetectors;
A signal processing circuit unit for outputting signals obtained by the first to third photodetectors to the outside,
The first photodetector is divided into two in the tangential direction, and is divided into four by being divided in two in a direction orthogonal to the tangential direction, and is arranged on the second photodetector side. Two light receiving areas, and third and fourth light receiving areas arranged on the third photodetector side,
The second photodetector is divided into two in the tangential direction and divided into four by being divided into two in the direction perpendicular to the tangential direction, and is arranged on the opposite side to the first photodetector side. 5 and 6 light receiving areas, and 7th and 8th light receiving areas arranged on the first photodetector side,
The third photodetector is divided into two in the tangential direction, and is divided into four by being divided into two in the direction orthogonal to the tangential direction, and is arranged on the first photodetector side. 10 light receiving regions and eleventh and twelfth light receiving regions disposed on the opposite side of the first photodetector side,
The signal processing circuit unit includes a fifth light receiving region of the second photodetector and the fifth light receiving region arranged on the same side as the first light receiving region of the first photodetector with respect to the tangential direction. A first output signal line to which a signal obtained from the ninth light receiving region of the three photodetectors is connected and output to the outside;
The sixth light receiving region of the second photodetector and the third light detector of the third photodetector disposed on the same side as the second light receiving region of the first photodetector and the tangential direction. A second output signal line to which signals obtained from 10 light receiving regions are connected and output to the outside;
The seventh light receiving region of the second photodetector and the third light detector of the third photodetector disposed on the same side as the second light receiving region of the first photodetector with respect to the tangential direction. A third output signal line to which signals obtained from 11 light receiving areas are connected and output to the outside;
The eighth light receiving region of the second photodetector and the third light detector of the third photodetector arranged on the same side as the first light receiving region of the first photodetector with respect to the tangential direction. A fourth output signal line to which signals obtained from the 12 light receiving areas are connected and output to the outside;
The signal processing circuit unit is controlled by the control unit to switch a signal connected to the first output signal line to a signal obtained from the fifth and sixth light receiving regions of the second photodetector, The signal connected to the second output signal line is switched to a signal obtained from the ninth and tenth light receiving regions of the third photodetector, and the signal connected to the third output signal line is changed to the signal The signals obtained from the seventh and eighth light receiving regions of the second photodetector are switched, and the signal connected to the fourth output signal line is changed to the eleventh and twelfth light receiving of the third photodetector. An optical disc apparatus having switching means for switching to a signal obtained from an area.

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