JP2005038582A - Information recording and reproducing device, and information recording and reproducing method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To solve the following problem; when the optical axis center of the light reflected to a photodetector in an optical head is deviated due to an adjustment error and a change in temperature, a recorded area and an unrecorded area of an optical disk differ in the offset of an objective lens position detection signal. <P>SOLUTION: A position detection signal correcting part 16 discriminates, based on an input RF signal, during search and track jump whether the present position on the optical disk 1 being reproduced is in a recorded area or in an unrecorded area, changing over an internal position detection signal adjusting part either to a recorded area adjusting part or to an unrecorded area adjusting part according to the result of the discrimination, thereby making both adjusting parts adjust the respective amplitudes and offsets to almost the same amplitude and offset for the position detection correcting signal in both of the recorded area and the unrecorded area, to output a position detection correcting output signal LES after the adjustment. At the time of seek operation, the correcting part 16 performs servo control in the tracking direction to the objective lens in the optical head 3 by using the position detection correcting output signal LES. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to an information recording / reproducing apparatus and information recording / reproducing method, and in particular, based on a position detection signal generated using one main beam and a pair of sub beams having a predetermined positional relationship with respect to the main beam. The present invention relates to an information recording / reproducing apparatus and information recording / reproducing method for recording and reproducing an information signal on a disk by the main beam while controlling the position of an objective lens of a head.

  To focus the light beam on the signal surface of the disc and focus it to record or reproduce information signals on a read-only optical disc, a recordable optical disc, a recordable / reproducible optical disc, etc. An optical head having the objective lens is used. The optical head has a configuration in which the objective lens can be displaced independently in a direction perpendicular to the signal surface of the optical disk (focus direction) and in a direction orthogonal to the track on the signal surface of the optical disk (tracking direction). Many are used. Such a mechanism for independently moving the objective lens in the two directions is called a biaxial actuator.

  Several specific configurations of the biaxial actuator are known. For example, a biaxial actuator having a structure in which an objective lens is supported by a leaf spring, a wire, or the like is known. As the driving force, an electromagnetic force generated by a coil and a magnet is used. FIG. 6 shows a cantilever type biaxial actuator supported by a leaf spring, a wire, or the like.

  In FIG. 6, the movable portion 20 composed of the objective lens 21 and its peripheral components is attached to each end of a pair of opposed leaf springs 22a and 22b. The other ends of the leaf springs 22a and 22b are attached to the fixing portion 23, respectively. The fixing part 23 is a fixing part of the optical head. FIG. 6A shows a state where the biaxial actuator is at a mechanical midpoint position. As shown by the arrows in FIG. 6A, the objective lens 21 can be displaced in the left-right direction in the figure.

  During the seek operation, the optical head moves at a high speed toward a desired position on the optical disk. In that case, the movable portion 20 moves relative to the fixed portion 23 by its own weight as shown in FIG. FIG. 6B shows a case where the optical head moves in the left direction in the figure, and thereby shows a case where the movable portion 20 swings all the way to the right.

In the case shown in FIG. 6B, the movable part 20 collides with another member, and as a result, the focus drive is hindered and the focus servo may be lost.
In addition, after the movement, it is necessary to wait for the tracking to be settled until the vibration of the movable portion 20 settles down. This becomes a problem when high speed movement is required.

  As one method for solving such a problem, a sensor for detecting the position of the movable unit 20 in the tracking direction with respect to the fixed unit 23 is provided so that the output of the sensor becomes a constant value corresponding to the mechanical midpoint position. There is a method of applying servo to the optical head. However, since such a method requires a sensor, problems such as an increase in the number of components such as a sensor, restrictions on mechanical design, and inhibition of downsizing of the optical head occur.

  On the other hand, the detection signal corresponding to the position fluctuation of the objective lens is formed by forming a difference between the tracking error signal formed by the DPP (Differential Push-Pull) method and the push-pull signal without using a position sensor. And an information recording / reproducing apparatus that controls the position of the objective lens to the midpoint position during a seek operation based on this detection signal has been proposed (for example, see Patent Document 1).

  FIG. 7 shows an example of a circuit for forming the tracking error signal TE by the DPP method described in Patent Document 1. Further, in the conventional information recording / reproducing apparatus described in Patent Document 1, one main beam and a pair of sub beams are approximately perpendicular to the longitudinal direction of the track on the optical disc. N + (1/2) track pitch (N: integer) is arranged, and the reflected light of the main beam from the optical disk is converted to that of the quadrant photo detector shown in FIGS. 9 (A) and 9 (B). A first two-divided photodetector having light receiving portions 80e and 80f shown in FIGS. 9A and 9B, which are received by the light receiving portions 80a to 80d and reflected light from the optical disk of the two sub-beams; Light is separately received by a second two-part photodetector having light receiving portions 80g and 80h.

  Here, detection signals Sa to Sd having levels according to the light intensity and the light receiving area of the light spot 81 of the reflected light of the main beam respectively received by the light receiving portions 80a to 80d of the four-divided photodetector are described. Detection having a level corresponding to the light intensity and light receiving area of the reflected light spots 82 and 83 of the two sub-beams received by the light receiving portions 80e and 80f and 80g and 80h of the two split photodetectors, respectively. If the signals are Se and Sf and Sg and Sh, the detection signals Se and Sf are supplied to the subtraction circuit 31 shown in FIG. 7, and an output signal corresponding to the difference (Se−Sf) is formed.

  Further, the detection signals Sb + Sc and Sa + Sd are supplied to the subtraction circuit 32, and an output signal corresponding to the difference {(Sa + Sd) − (Sb + Sc)} is formed. The subtraction circuit 33 is supplied with the detection signals Sh and Sg, and an output signal corresponding to the difference (Sg−Sh) is formed.

  The output signal of the subtraction circuit 31 and the output signal of the subtraction circuit 33 whose gain has been adjusted by the gain adjustment circuit 35 are supplied to the addition circuit 34. Therefore, when the gain of the gain adjusting circuit 35 is expressed as K1, the output signal of the adding circuit 34 is {(Se−Sf) + K1 (Sg−Sh)}. The output signal of the adding circuit 34 is supplied to the subtracting circuit 39 via the gain adjusting circuit 36 (gain is set to K2). An output signal of the subtraction circuit 32 is supplied to the subtraction circuit 39. Therefore, the tracking error signal TE output from the subtraction circuit 39 is as shown in the following equation.

TE = (Sa + Sd) − (Sb + Sc) −K2 [(Se−Sf)
+ K1 (Sg-Sh)]
In the above equation, (Sa + Sd) − (Sb + Sc) is a push-pull signal based on zero-order light, and (Se−Sf) and (Sg−Sh) are push-pull signals based on ± primary light, respectively. Therefore, the offset can be removed from the tracking error signal TE by selecting the gains K1 and K2 so as to correct the difference in the amplitude of the push-pull signal.

  FIG. 8 shows a position detection signal generation circuit in the conventional information recording / reproducing apparatus described in Patent Document 1. Signals from terminals 37 and 38 in the circuit for forming the tracking error signal TE shown in FIG. 7 are supplied to input terminals 37 and 38, respectively. That is, the push-pull signal (Sa + Sd) − (Sb + Sc) is supplied to the input terminal 37, and the signal K2 [(Se−Sf) + K1 (Sg−Sh)] is supplied to the input terminal 38.

  These signals are supplied to the subtraction circuit 41. Since the subtraction circuit 41 performs the same subtraction process as the subtraction circuit 39, the subtraction circuit 41 obtains the same signal as the tracking error signal TE described above. The output signal of the subtracting circuit 41 is supplied to the subtracting circuit 43 via the 1/2 attenuation circuit 42. A push-pull signal from the input terminal 37 is supplied to the subtraction circuit 43.

  Thereby, the output signal of the subtraction circuit 43 is expressed by the following equation.

(Sa + Sd)-(Sb + Sc) -1 / 2.TE
= 1/2 · [(Sa + Sd) − (Sb + Sc)]
+ 1/2 · K2 [(Se−Sf) + K1 (Sg−Sh)]
As can be seen from the above equation, the component corresponding to the position of the objective lens included in the zero-order light push-pull signal and the component corresponding to the position of the objective lens included in the ± first-order light push-pull signal are added. The position detection signal LE at a level corresponding to the position of the objective lens can be output from the subtraction circuit 43 to the output terminal 44.

JP-A-11-250475 (pages 4-7, FIG. 3, FIG. 7, FIG. 8)

  However, in the above-described conventional information recording / reproducing apparatus, the vertical division lines of the four-divided photodetector and the two two-divided photodetectors constituting the photodetector 80, the reflected light spot 81 of the main beam, and the sub-beam reflected light. The centers of the optical axes of the spots 82 and 83 are adjusted so as to coincide with each other. However, due to adjustment errors and temperature changes, the optical axis centers are laterally changed as shown in FIGS. 9A to 9B. May be displaced (hereinafter referred to as optical axis deviation).

  10A shows the main beam push-pull signal MPP, and FIG. 10B shows the sub-beam push-pull signal SPP. Here, the irradiation light amounts of the two sub beams are assumed to be equal. FIG. 10C shows a DPP signal, which is a signal obtained by subtracting the sub-beam bushing pull signal SPP from the main beam push-pull signal MPP. Further, FIG. 10D shows a position detection signal LE, which is a signal obtained by adding the main beam push-pull signal MPP and the sub beam push-pull signal SPP.

  The left part (a) of each signal waveform shown in FIGS. 10A to 10D is an unrecorded area, and the right part (b) is a recorded area when each beam is irradiated. It is an example of a waveform. Each signal waveform in FIG. 10 is in a state where the optical axis is shifted, and a DC offset component A is generated in the unrecorded area and a DC offset component B is generated in the recorded area.

  In the DPP signal shown in FIG. 10C, even if a DC offset component occurs in the main beam push-pull signal MPP and the sub-beam push-pull signal SPP, the DC offset component is canceled, so that the DC offset is applied to the unrecorded area and the recorded area. Does not occur. However, in the position detection signal LE shown in FIG. 10D, a DC offset component is added to generate a DC offset component of 2A in the unrecorded area and 2B in the recorded area. The problem is that the DC offset level is different between the unrecorded area and the recorded area.

  FIG. 4 shows a position detection signal LE when the objective lens is shifted by an appropriate frequency (for example, a frequency of 20 Hz and a displacement of about 300 μm) when there is an optical axis shift.

  4A is a position detection signal LE when the lens portion of the arrow in FIG. 4A on the right side is shifted, and is a position detection signal of an unrecorded area. A DC offset component 2A is generated. (B) on the left side of FIG. 4 is a position detection signal LE for a recorded area when the portion indicated by the arrow in (B) on the right side of FIG. 4 is lens-shifted, and is a position detection signal for the recorded area. A DC offset component 2B is generated. (C) on the left side of FIG. 4 is a position detection signal LE when the portion indicated by the arrow (C) on the right side of FIG. 4 is lens-shifted, and is a position detection signal at the end of recording and recording. The DC offset component 2A is generated in the unrecorded area, and the offset component 2B is generated in the recorded area. An offset of 2A-2B occurs at the boundary between the recorded area and the unrecorded area.

  Even when the optical axis center is deviated, the position detection signal proposed in the above-mentioned Patent Document 1 is particularly problematic if the position detection signal is offset when the optical disk is all recorded or not recorded. However, when the recorded area and the unrecorded area are mixed, there is a problem that the offset of the position detection signal varies between the recorded area and the unrecorded area.

  In addition, when there is a defect on the recording medium, the reflected light does not return, so the main beam push-pull signal MPP and the sub beam push-pull signal SPP cannot detect an error signal. Since the position detection signal LE is a signal obtained by calculating the main beam push-pull signal MPP and the sub beam push-pull signal SPP, there is another problem that the position detection signal LE cannot detect an error signal.

  The signal waveform of (E) on the left side of FIG. 4 indicates that the objective lens has an appropriate frequency (for example, an unrecorded area) on the recording medium indicated by (E) and (F) on the right side of FIG. The position detection signal LE when the lens is shifted as indicated by a bidirectional arrow at a frequency of 20 Hz and a displacement of about 300 μm is shown. As shown in the position detection signal LE waveform shown in FIG. 4E, it can be seen that the position detection signal LE cannot be detected when passing through the defect area.

  That is, a recorded area and an unrecorded area are mixed even if an attempt is made to hold the objective lens at the midpoint position by servo-controlling the biaxial actuator during the seek operation in the tracking direction by the position detection signal LE. For optical discs or optical discs with defective areas, the offset of the position detection signal fluctuates, so that the objective lens may be shaken out and focus control may be hindered, and tracking pull-in after the seek operation ends becomes unstable. .

  The present invention has been made in view of the above points, and in a recording medium in which recorded areas and unrecorded areas are mixed, or in an information recording / reproducing apparatus having a defective area and whose optical axis center is shifted. An object of the present invention is to provide an information recording / reproducing apparatus and an information recording / reproducing method capable of suppressing a fluctuation of a position detection signal generated from a difference between a tracking error signal and a push-pull signal and thereby enabling a suitable seek operation.

  In order to achieve the above object, the information recording / reproducing apparatus according to the first aspect of the present invention is characterized in that each spot of the two sub beams formed on the recording medium is different from the spot of the main beam formed on the recording medium. The positions are separated in the opposite direction by approximately N + (1/2) track pitch (N: integer) in the direction perpendicular to the longitudinal direction of the upper track, and are separated from each other by a predetermined distance in the opposite direction in the longitudinal direction of the track. In this way, one main beam and two sub-beams are simultaneously irradiated through the objective lens, and the resulting reflected light from the recording medium of one main beam and two sub-beams is received by the photodetector through the objective lens. A tracking error signal is generated based on the received light signal, and the irradiation position on the recording medium of one main beam and two sub beams is detected. In an information recording / reproducing apparatus for recording / reproducing information on / from a recording medium, an optical head for generating a position detection signal is generated based on a light reception signal of reflected light of the main beam obtained by the optical head. A recording / unrecording discriminating means for discriminating whether the irradiation position is a recorded area or an unrecorded area on the recording medium, and the irradiation position on the recording medium of one main beam and two sub-beams are the length of the track on the recording medium. Lens shift means for displacing the position of the objective lens so as to shift a certain amount in a direction perpendicular to the direction, and a position detection signal output from the optical head when the position of the objective lens is displaced by the lens shift means. On the other hand, the recorded area adjustment unit for adjusting the amplitude and offset for the recorded area, and the amplitude and offset for the unrecorded area A position detection signal adjustment unit including an adjustment unit for an unrecorded area to be adjusted, and a recorded region adjustment unit of the position detection signal adjustment unit when the irradiation position of the main beam is determined to be a recorded region by the recording / unrecording determination unit Is selected as a position detection correction signal, and when the irradiation position of the main beam is determined to be an unrecorded area by the recording / unrecording determining means, the unrecorded area adjusting section of the position detection signal adjusting means A selection unit that selects the adjusted position detection signal as a position detection correction signal, and the amplitude and offset of the position detection correction signal selected by the selection unit are detected, and the detection signal is supplied to the position detection signal adjustment unit. Position detection signal adjusting means so that the amplitude and offset of the correction signal for position detection are almost the same amplitude and offset in the recorded area and the unrecorded area And a position detection correction signal detection means for adjusting the position of the objective lens, and performing servo control in the direction perpendicular to the longitudinal direction of the track with respect to the objective lens using the position detection correction signal during the seek operation.

  In order to achieve the above object, an information recording / reproducing method according to a second aspect of the present invention is an information recording / reproducing method in which information is recorded on and reproduced from a recording medium by the optical head. A first step of displacing the position of the objective lens such that the irradiation positions of the two sub-beams on the recording medium are shifted by a certain amount in a direction perpendicular to the longitudinal direction of the track on the recording medium; Second, adjusting the amplitude and offset for the recorded area and adjusting the amplitude and offset for the unrecorded area with respect to the position detection signal output from the optical head when the position of the objective lens is displaced by And the irradiation position of the main beam on the recording medium is recorded on the recording medium based on the received signal of the reflected light of the main beam obtained by the optical head. A third step for discriminating whether the area is an area or an unrecorded area; and if the irradiation position of the main beam is determined to be a recorded area by the third step, the amplitude and offset adjustment for the recorded area is performed by the second step. When the detected position detection signal is selected as a position detection correction signal, and the irradiation position of the main beam is determined to be an unrecorded area in the third step, the amplitude and offset adjustment for the unrecorded area is performed in the second step. The fourth step of selecting the detected position detection signal as the position detection correction signal, and the amplitude and offset of the position detection correction signal selected by the fourth step are detected, and the second is determined based on the detection signal. Adjust the amplitude and offset of the position detection correction signal in this step so that the recorded area and the unrecorded area have almost the same amplitude and offset. That first it includes fifth and steps, and performs servo control in the vertical direction to the longitudinal direction of the track with respect to the objective lens by using a position detection correction signal during a seek operation.

  In the information recording / reproducing apparatus and information recording / reproducing method of the present invention, even when the center of the optical axis is shifted due to an adjustment error, a temperature change, or the like, a recording medium in which recorded areas and unrecorded areas are mixed is used. When the seek operation is performed, adjustment is performed so that the amplitude and offset of the position detection correction signal are almost the same in the recorded area and the unrecorded area, so the actuator is tracked by the position detection correction signal. By performing servo control in the direction (perpendicular to the longitudinal direction of the track on the recording medium), the objective lens can always be held at the midpoint position of the actuator even during a seek operation.

  According to the present invention, even when the optical axis center of the reflected light with respect to the light receiving unit in the optical head is shifted due to an adjustment error, a temperature change, etc., the recording medium in which the recorded area and the unrecorded area are mixed is provided. When the seek operation is performed, adjustment is performed so that the amplitude and offset of the position detection correction signal are almost the same in the recorded area and unrecorded area, and the actuator is tracked in the tracking direction using the position detection correction signal. Since the objective lens is always held at the midpoint position of the actuator during the seek operation, the objective lens can be prevented from shaking during the seek operation, preventing the focus control from being hindered. In addition, tracking pull-in after the end of the seek operation can be stabilized.

  Further, according to the present invention, the tracking error signal does not include an offset, and accurate tracking control is possible.

  Next, an embodiment of the present invention will be described with reference to the drawings. FIG. 1 shows a configuration diagram of an embodiment of an information recording / reproducing apparatus according to the present invention. In FIG. 1, an optical disk 1 is a recordable / reproducible optical disk, for example, a phase change type optical disk, and is driven by a CLV (constant linear velocity) method having a constant linear velocity or a CAV (constant angular velocity) having a constant rotation speed. ) Method. An optical head 3 is provided for recording data on the optical disc 1 and for reproducing data from the optical disc 1.

  Similar to the optical head in the conventional information recording / reproducing apparatus described in Patent Document 1, the optical head 3 has two main sub-beam spots on one side of the optical disk 1 during recording and reproduction. Are separated from each other by about N + (1/2) track pitch (N: integer) in a direction perpendicular to the longitudinal direction of the track on the optical disk, and opposite to each other in the longitudinal direction of the track with respect to the spot position of the main beam. A main beam and a pair of sub beams are simultaneously irradiated through an objective lens supported by a biaxial actuator so as to be at a predetermined distance from each other, and each reflected light from the optical disc 1 of the one main beam and the pair of sub beams is irradiated. The light is received by the photodetector through the objective lens and the same as the conventional device based on these received light signals. To generate a tracking error signal in the known arrangement for generating a position detection signal corresponding to the position of the objective lens.

  Data from an external host processor is supplied to the write channel unit 14 via a signal processing unit 10 including an ECC (error correction) encoder, ECC decoder, buffer controller, and host interface. A buffer memory 11 is connected to the signal processing unit 10. Write data from the host processor is stored in the buffer memory 11 via an interface connector (not shown) and the signal processing unit 10. The write channel unit 14 performs processing such as conversion of write data into a sector structure, addition of a frame synchronization signal, and digital modulation.

  Recording data from the write channel unit 14 is supplied to the laser driver 15. The laser driver 15 generates a drive waveform having a predetermined level relationship for recording record data on the optical disc 1. The output signal of the laser driver 15 is supplied to the optical head 3, where the light intensity of the main beam is modulated, and the main beam is irradiated in focus on the signal surface of the optical disc 1 by the objective lens to record data.

  A detection signal obtained by photoelectrically converting the reflected light of the main beam and the sub beam from the optical disk 1 by the optical head 3 is supplied to the RF amplifier 4. The RF amplifier 4 calculates detection signals respectively generated from the divided photodetectors in the optical head 3, and generates an RF signal, a tracking error signal TE, a focus error signal FE, and a position detection signal LE. The position detection signal LE is further input to the position detection signal correction unit 16, where it is used as a position detection correction output signal LES.

  These signals are supplied to the read channel servo unit 5. The read channel servo section 5 generates a control signal for controlling the biaxial actuator that supports the objective lens in the optical head 3 based on the tracking error signal TE, the focus error signal FE, and the position detection correction output signal LES. This control signal is supplied to the biaxial actuator via the biaxial driver 6. The RF amplifier 4 receives a detection signal corresponding to the laser power generated by the semiconductor laser in the optical head 3 and performs known laser power control for controlling the laser power to an appropriate value.

  The read channel servo unit 5 generates a control signal for the spindle driver 7 that drives the spindle motor 2. In response to this control signal, the spindle motor 2 rotates the optical disk 1 with CAV or CLV. Further, the read channel servo section 5 also generates a control signal for the thread driver 9 that drives the thread motor 8. With this control signal, the sled motor 8 moves the optical head 3 in the radial direction of the optical disc 1.

  During a seek operation in which the optical head 3 is moved at a high speed to a desired track position on the optical disk 1 by the thread motor 8, the objective lens is moved in the tracking direction so that the main beam follows the desired track by the tracking error signal TE. The tracking servo for controlling the position is stopped, and the biaxial actuator is servo-controlled in the tracking direction in accordance with the position detection signal of the objective lens. In the present embodiment, the above-described 2 By servo-controlling the axis actuator in the tracking direction, the objective lens is always held at the midpoint position during seek operation even for the optical disc 1 in which unrecorded areas and recorded areas are mixed or defective. It is what you do.

  At the time of reproduction, the read channel servo unit 5 obtains reproduction data from the RF signal input from the RF amplifier 4 and supplies this to the signal processing unit 10. A buffer memory 11 is connected to the signal processing unit 10. The reproduction data from the signal processing unit 10 is sent to the host processor via an interface connector (not shown).

  In order to control the operation of the entire drive, a system controller 12 composed of an MPU (micro processing unit) is provided. A ROM (Read Only Memory) 13 for storing programs is connected to the system controller 12.

  The present invention is characterized by the configuration of the position detection signal correction unit 16. Next, the configuration and operation of the position detection signal correction unit 16 will be described. FIG. 2 shows a block diagram of an embodiment of the position detection signal correction unit 16 of the main part of the present invention. As shown in the figure, the position detection signal correction unit 16 receives the position detection signal LE and the RF signal as input signals, and records / unrecorded determination unit 161, lens shift unit 162, position detection signal detection unit 163, position detection signal. The adjustment unit 164 and the position detection signal selection unit 165 are configured to output a position detection correction output signal LES and a lens shift signal LS.

  Here, the above-mentioned recording / unrecording discriminating unit 161 determines whether the area where the main beam is currently irradiated on the optical disc 1 shown in FIG. The determination is made based on the amplitude of the RF signal obtained by the conversion. For example, since the RF signal in the recording area has an amplitude of 2V to 2.5V, and the RF signal in the unrecorded area has an amplitude in the vicinity of 2.5V, a known bottom hold signal is created from the RF signal. It is possible to determine whether the area is a recorded area or an unrecorded area.

  The lens shift unit 162 outputs a lens shift signal LS for shifting the objective lens in the optical head 3 by a certain amount in the radial direction of the optical disc 1 based on the control signal from the system controller 12 shown in FIG. By the lens shift described above, the irradiation position on the optical disc 1 of one main beam and two sub beams is shifted in the direction perpendicular to the longitudinal direction of the track on the optical disc 1 (tracking direction). The objective lens position displacement control method based on the control signal is the same as the objective lens position displacement control method based on the tracking error signal. The position detection signal detection unit 163 detects the amplitude and offset of the position detection signal from the position detection signal detected when the lens is shifted.

  The position detection signal adjustment unit 164 includes a recorded region position detection signal adjustment unit and an unrecorded region position detection signal adjustment unit. Based on the signal detected by the position detection signal detection unit 163, the position detection signal adjustment unit 164 The position detection signal LE is adjusted to the same amplitude and offset in the unrecorded area. The position detection signal selection unit 165 selects the recorded position detection signal when the recorded / unrecorded determining unit 161 determines that the recorded area is moving, and detects the unrecorded position when it is determined that the last recorded area is moving. This is a switch circuit that selects a signal and outputs the selected signal as a position detection correction output signal LES.

  Next, the operation of the embodiment of the position detection signal correction unit 16 shown in FIG. 2 will be described in detail with reference to the flowchart of FIG. The operation according to the flowchart of FIG. 3 is performed during reproduction. First, with the focus servo turned on (step S1), the recording / non-recording discriminating unit 161 determines the irradiation position of the main beam from the optical head 3 on the optical disc 1 based on the RF signal reproduced from the optical disc 1. It is determined whether it is in a recorded area or an unrecorded area (step S2). Here, in order to correct the position detection signal LE in each of the recorded area and the unrecorded area, a position detection signal adjustment section for each of the recorded area and the unrecorded area is mounted in the position detection signal adjustment section 164. Yes.

  If it is determined in step S2 that the current position is in the recorded area, the recorded / unrecorded discriminating section 161 so that the position detection signal selecting section 165 selects the position detection signal of the recorded area of the position detection signal adjusting section 164. (Step S3).

  Subsequently, a lens shift signal LS is output from the lens shift unit 162, and the objective lens is lens-shifted by a sine wave of a certain amount (for example, a frequency of 20 Hz, displacement of about 300 μm) (step S4), and the position detection at that time is detected. The signal LE is detected as a position detection signal of the recorded area by the position detection signal detection unit 163 so that an amplitude A and an offset B (for example, an amplitude of 1 Vpp and an offset center of 1.65 V) predetermined by the lens shift amount are obtained. The position detection signal adjustment unit for recorded area in the position detection signal adjustment unit 164 performs amplitude adjustment and offset adjustment of the position detection signal LE, and the adjusted position detection signal is used as a position detection correction output signal LES for the recorded area. Output (step S5).

  After the above adjustment, it is determined whether or not the position detection signal LE has been adjusted in the unrecorded area (step S6). At this time, since the position detection signal has not been adjusted in the unrecorded area, the unrecorded area is adjusted. That is, the thread driver 9 of FIG. 1 is driven by the read channel servo unit 5 to move the main beam irradiation position of the optical head 3 to the unrecorded area of the optical disc 1 and the unrecorded area in the position detection signal adjusting unit 164. The recorded / unrecorded discriminating unit 161 controls the position detection signal selecting unit 165 to select the output signal of the position detection signal adjusting unit for use (step S7).

  Subsequently, a lens shift signal LS is output from the lens shift unit 162, and the objective lens is lens-shifted by a sine wave of a certain amount (for example, a frequency of 20 Hz, displacement of about 300 μm) (step S8), and position detection at that time is detected. The signal LE is detected by the position detection signal detection unit 163, and the position detection signal adjustment unit 164 has an amplitude A and an offset B (for example, an amplitude of 1 Vpp and an offset center of 1.65 V) determined in advance by the lens shift amount. The position detection signal adjustment unit for unrecorded area adjusts the amplitude and offset of the position detection signal LE, and outputs the adjusted position detection signal as the position detection correction signal LES for the unrecorded area (step S9).

  Subsequently, after the above adjustment, it is determined whether or not the position detection signal LE has been adjusted in the recorded area (step S10). At this stage, since the position detection signal LE has already been adjusted in the recorded area in step S5, the adjustment is completed.

  If it is determined in step S2 that the area is not a recorded area, that is, it is an unrecorded area, the process proceeds to step S7, and the output signal of the position detection signal adjustment section for the unrecorded area in the position detection signal adjustment section 164 is output. The recording / non-recording discriminating unit 161 controls the position detection signal selecting unit 165 to select. Also in this case, the lens shift is performed on both the recorded area and the unrecorded area, the position detection signal LE at that time is detected by the position detection signal detection unit 163, and the amplitude A and the offset determined in advance by the lens shift amount are detected. The position detection signal adjustment unit 164 performs amplitude adjustment and offset adjustment of the position detection signal LE so as to be B (for example, amplitude 1 Vpp, offset center 1.65 V).

  The position detection signal correction unit 16 determines whether the currently reproduced location is the recorded area or the end recording area by the recording / unrecording determination unit 161 during the search or track jump, and the position detection signal according to the determination result. The selection unit 165 is switched so as to select either the output signal of the recorded region position detection signal adjustment unit in the position detection signal adjustment unit 164 or the output signal of the unrecorded region position detection signal adjustment unit, The detection correction output signal LES is supplied to the read channel servo unit 5.

  Next, a method for shifting the lens by a certain amount by the lens shift signal from the lens shift unit 162 will be described. By simply shifting the lens at a constant voltage, an error occurs in the lens shift amount due to variations in actuator sensitivity, aging, aging, etc., so in this embodiment, the lens shift amount is set to the number of tracking errors (tracking error). It is obtained by counting a certain number of tracks). That is, the read channel servo unit 5 in FIG. 1 obtains the lens shift amount from the number of tracks in which a tracking error has occurred during lens shift of the objective lens.

  In order to obtain the lens shift amount from the number of tracks in which a tracking error has occurred, first, the eccentricity amount of the optical disc 1 is obtained from the number of tracks in which a tracking error has occurred (track count value) before reproduction or recording. The number of tracks Cd in which a tracking error has occurred during one rotation period Td of the optical disk 1 in the focus ON state is obtained by counting. Next, the lens shift is performed at a constant period T1 and voltage V, and the number of tracks C1 in which a tracking error occurs in period T1 is obtained. The lens shift amount can be obtained by substituting the number of tracks in which the tracking error has occurred (track count value) into the following equation.

Lens shift amount = Tp × (track count value excluding eccentricity component / 2)
= Tp * {(C1-Cd * (T1 / Td)) / 2}
In the above formula, Tp represents the track pitch on the optical disc 1.

  Thereafter, the lens shift amount is calculated by changing the voltage V for lens shift and counting the number of tracks in which tracking errors have occurred in the same manner so that the lens shift amount obtained by the above formula becomes the desired lens shift amount. Good.

  FIG. 4D shows the position detection correction output signal LES generated by the present embodiment. As shown in FIG. 4D, the position detection correction output signal LES of the present embodiment when straddling the recorded area and the unrecorded area is like the position detection signal LE shown in FIG. It can be seen that no offset and amplitude variations have occurred.

  Next, the configuration and operation of another embodiment of the position detection signal correction unit 16 will be described. FIG. 5 shows a block diagram of another embodiment of the position detection signal correction unit 16 as the main part of the present invention. In the figure, the same components as those in FIG. The position detection signal correction unit 16 shown in FIG. 5 includes a position detection signal hold unit 166, a defect detection unit 167, and a defect position detection signal selection unit in addition to the configuration of the position detection correction unit according to the embodiment shown in FIG. 168 is further provided to output a position detection correction output signal LES and a lens shift signal LS, and the objective lens in the optical head is always held at the midpoint position even when the main beam passes through the defective portion of the recording medium. It is made to be able to. In the embodiment of FIG. 5, the position detection signal selection unit 165 outputs a position detection correction signal LE1 (same as LES in FIG. 2).

  In FIG. 5, a position detection signal hold unit 166 is a hold circuit that samples and holds the position detection correction signal LE1 output from the position detection signal selection unit 165 at a constant interval and outputs a position detection correction hold signal LE1H. The defect detection unit 167 determines whether the region where the main beam is currently irradiated on the optical disc 1 shown in FIG. 1 is a defect region, and determines the peak value of the RF signal obtained by photoelectrically converting the reflected light of the main beam. Based on the determination.

  For example, when there is no defect, the peak value of the RF signal is about 2.5 V regardless of the recorded area and the unrecorded area as described above. On the other hand, if there is a defect, the peak value of the RF signal from the defective area is about 1.7 V, which is lower than the bottom value of the RF signal in the recorded area. Accordingly, when the level is, for example, 2.0 V or less, a known peak hold circuit is detected as a defective area. The defect position detection signal selection unit 168 receives the position detection correction signal LE1 output from the position detection signal selection unit 165 and the position detection signal held by the position detection signal hold unit 166 based on the defect detection signal from the defect detection unit 167. This is a selection circuit that selects one of the correction hold signals LE1H and outputs it as a position detection correction output signal LES.

  In this embodiment, when there is a defect on the optical disc 1, the position detection correction hold signal LE1H held by the position detection signal hold unit 166 is selected by the defect detection signal from the defect detection unit 167, and the optical disc 1 If there is no defect above, no defect detection signal is input from the defect detection unit 167, so the position detection correction signal LE1 is selected, and the selected position detection correction signal LE1H or LE1 is used as the position detection correction output signal LES as a read channel.・ Supply to servo section 5.

  FIG. 4F shows the position detection correction output signal LES generated by the present embodiment when it passes through the defect area. The position held by the position detection signal hold 166 when the main beam passes through the defect portion. Since the detection correction hold signal LE1H is output as the position detection correction output signal LES, the position detection correction output signal LES can be output without being lost even when the main beam passes through the defective portion.

  As described above, the position detection correction output signal LES of the objective lens generated by the position detection signal correction unit 16 having the configuration shown in FIG. 2 or 5 is used for the biaxial actuator in the optical head 3 during the seek operation. By performing servo control in the tracking direction, even if the main beam from the objective lens supported as shown in FIG. 6 by the biaxial actuator straddles the recording area, the unrecorded area, or passes through the defective portion, the objective lens is moved. It can always be held at the midpoint position.

  With this type of servo (midpoint servo), the objective lens does not swing out in one direction when the optical head moves during the seek operation, which solves the problem of hindering focus drive during the seek operation. In addition, tracking can be quickly and stably performed after the seek operation is completed.

  In the above embodiment, the case where the defect on the recording medium is in the unrecorded area has been described. However, even when the defect is at the boundary between the recorded area and the unrecorded area and the recorded area, the above-described embodiment is performed. Of course, the objective lens can always be held at the midpoint position by the same operation as the embodiment. In addition, if there is a defect on the recording medium, the position detection signal cannot be detected even if the optical axis center of the reflected light with respect to the light receiving part in the optical head is not shifted, so the defect of the present invention is detected. Thus, a method of holding the position detection signal is effective.

It is a block diagram which shows one Embodiment of the information recording / reproducing apparatus of this invention. It is a block diagram of one Embodiment of the position detection signal correction | amendment part in the information recording / reproducing apparatus of this invention. It is a flowchart for correction | amendment operation | movement description of the position detection signal correction | amendment part of one Embodiment in this invention. A position detection signal LE, a position detection correction signal LE1, a position detection correction signal LE1 when passing through the missing area, and a position detection correction output signal LES corrected for defects when there is an optical axis shift and the lens is shifted. FIG. It is a block diagram of other embodiment of the position detection signal correction | amendment part in the information recording / reproducing apparatus of this invention. It is a block diagram of the biaxial actuator used for description of the problem of the conventional information recording / reproducing apparatus. It is a circuit diagram of an example of the tracking error signal formation circuit by DPP method in the conventional apparatus. It is a circuit diagram of an example of the position detection signal generation circuit in the conventional apparatus. In the conventional apparatus, it is a figure which shows the light-receiving surface and beam light-receiving position of a photodetector when there is optical axis deviation and when there is no optical axis deviation. It is explanatory drawing of each error signal of MPP, SPP, DPP, and LE when there is an optical axis shift.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Optical disk 3 Optical head 4 RF amplifier 5 Read channel servo part 6 Driver 8 Thread motor 9 Thread driver 10 Signal processing circuit 11 Buffer memory 12 System controller 14 Light channel part 16 Position detection signal correction | amendment part 161 Recording non-recording discrimination | determination part 162 Lens Shift section 163 Position detection signal detection section 164 Position detection signal adjustment section 165 Position detection signal selection section LE Position detection signal LE1H Position detection correction hold signal LE1 Position detection correction signal LES Position detection correction output signal LS Lens shift signal

Claims (2)

With respect to the spot of the main beam formed on the recording medium, each spot of the two sub beams formed on the recording medium is approximately N + (1 in the direction perpendicular to the longitudinal direction of the track on the recording medium. / 2) One main beam and two sub-beams are passed through the objective lens so that they are separated in the opposite direction by the track pitch (N: integer) and separated from each other by a predetermined distance in the opposite direction in the longitudinal direction of the track. A tracking error signal is generated based on a light reception signal obtained by simultaneously irradiating each reflected light from the recording medium of the one main beam and two sub-beams generated by the light beam through the objective lens. And position detection corresponding to the irradiation position on the recording medium of the one main beam and the two sub beams. Comprising an optical head for generating a signal, in the information recording and reproducing apparatus for recording and reproducing information on the recording medium,
Recording / non-recording for determining whether the irradiation position of the main beam on the recording medium is a recorded area or an unrecorded area on the recording medium based on a light reception signal of the reflected light of the main beam obtained by the optical head Discrimination means;
The position of the objective lens is displaced so that the irradiation position of the one main beam and the two sub beams on the recording medium is shifted by a certain amount in a direction perpendicular to the longitudinal direction of the track on the recording medium. Lens shift means;
A recorded area adjustment unit that adjusts the amplitude and offset for a recorded area with respect to the position detection signal output from the optical head when the position of the objective lens is displaced by the lens shift unit; Position detection signal adjustment means including an unrecorded area adjustment unit for adjusting the amplitude and offset for the unrecorded area;
When the irradiation position of the main beam is determined to be the recorded area by the recording / non-recording determination means, the position detection signal adjusted by the recorded area adjustment unit of the position detection signal adjustment means is position detection corrected. When the main beam irradiation position is determined to be the non-recorded area by the recording / non-recording determining means, the position detection adjusted by the unrecorded area adjusting unit of the position detection signal adjusting means is selected as a signal. Selecting means for selecting the signal as a position detection correction signal;
The amplitude and offset of the position detection correction signal selected by the selection means are detected, and the detection signal is supplied to the position detection signal adjustment means, and the amplitude and offset of the position detection correction signal are recorded. A position detection correction signal detection means for adjusting the position detection signal adjustment means so that the area and the unrecorded area have substantially the same amplitude and offset, and the position detection correction signal is used for the objective lens during the seek operation. An information recording / reproducing apparatus that performs servo control in a direction perpendicular to the longitudinal direction of the track. With respect to the spot of the main beam formed on the recording medium, each spot of the two sub beams formed on the recording medium is approximately N + (1 in the direction perpendicular to the longitudinal direction of the track on the recording medium. / 2) One main beam and two sub-beams are passed through the objective lens so that they are separated in the opposite direction by the track pitch (N: integer) and separated from each other by a predetermined distance in the opposite direction in the longitudinal direction of the track. A tracking error signal is generated based on a light reception signal obtained by simultaneously irradiating each reflected light from the recording medium of the one main beam and two sub-beams generated by the light beam through the objective lens. And position detection corresponding to the irradiation position on the recording medium of the one main beam and the two sub beams. An optical head for generating a signal, the information recording on a recording medium, the information recording and reproducing method for reproducing,
The position of the objective lens is displaced so that the irradiation position of the one main beam and the two sub beams on the recording medium is shifted by a certain amount in a direction perpendicular to the longitudinal direction of the track on the recording medium. A first step;
When the position of the objective lens is displaced by the first step, the amplitude and offset for the recorded area are adjusted with respect to the position detection signal output from the optical head, and for the unrecorded area A second step of adjusting amplitude and offset;
Based on a light reception signal of the reflected light of the main beam obtained by the optical head, a third position for determining whether the irradiation position of the main beam on the recording medium is a recorded area or an unrecorded area on the recording medium Steps,
When the irradiation position of the main beam is determined to be the recorded area in the third step, the position detection signal in which the amplitude and the offset for the recorded area are adjusted in the second step is subjected to position detection correction. When the main beam irradiation position is determined to be the unrecorded area by the third step, the position where the amplitude and the offset for the unrecorded area are adjusted by the second step is selected as a signal. A fourth step of selecting the detection signal as a position detection correction signal;
The amplitude and offset of the position detection correction signal selected in the fourth step are detected, and the adjustment of the amplitude and offset of the position detection correction signal in the second step is performed based on the detection signal. A fifth step of adjusting the recorded area and the unrecorded area to have substantially the same amplitude and offset, and using the position detection correction signal during a seek operation with respect to the longitudinal direction of the track with respect to the objective lens An information recording / reproducing method characterized by performing vertical servo control.

Images