JP2005285220A - Optical disk apparatus and control method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To make skew control efficient in an optical disk apparatus and a control method by which skew control is performed based on reflected light of an optical disk. <P>SOLUTION: A skew angle R1 near an inner periphery of a disk and a skew angle R2 near an outer periphery of the disk are obtained using a tracking error signal TE, R1 and R2 are connected by a straight line and a skew angle between the R1 and the R2 is supplemented. An offset table 32C corresponding a direction of the supplemented skew angle to an address od a disk 2 is generated. Then, when skew control is started, the optical pickup 4 is tilted in a direction of the predicted skew angle. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

The present invention relates to an optical disc apparatus and a control method for performing skew control based on reflected light of an optical disc.

  The reproduction signal RF of the optical disc apparatus has a high signal level when irradiated with lands, and a low signal level when irradiated with pits. Conventional optical disc apparatuses include an optical disc apparatus that performs skew control based on the signal level of the reproduction signal RF (see Patent Document 1). This utilizes the characteristic that if the skew control is good, the amount of light returned when pits are irradiated is reduced.

  By utilizing this characteristic, it can be determined that the skew angle at which the reproduction signal RF is minimum is the best skew angle. In order to detect the best point of the skew angle, the optical disk apparatus adjusts the skew angle so that the reproduction signal RF is minimized by changing the skew angle in the plus direction or the minus direction. The reproduction signal RF becomes minimum at a certain skew angle θ, and increases as the skew angle goes away from θ. With the reproduction signal RF, it is possible to detect whether or not the skew angle is shifted, but it is not possible to detect in which direction it is shifted. For this reason, if the skew angle is changed in the wrong direction, an error in the skew angle increases, and the aberration generated by this error may exceed the allowable aberration range.

  Further, when the skew angle error increases, the time required for adjusting the skew angle becomes longer, and the error amount increases. An increase in the amount of errors could have a significant impact that could not be realized as a system.

JP 2000-331364 A

  The present invention has been made in view of the above-described problems, and an object thereof is to provide an optical disc apparatus and a control method that make skew control efficient.

  In order to solve the above-described problems, an optical disc apparatus according to the present invention includes a laser beam irradiating unit that irradiates an optical disc with laser light, an inclination angle changing unit that changes an inclination angle of the laser beam irradiating unit with respect to the optical disc, A control means for controlling the tilt angle changing means so that a control value obtained from the reflected light becomes an extreme value, and a tilt angle at an arbitrary position of the optical disk based on the tilt angle of the laser light irradiation means at one or more positions of the optical disk. And a control unit that tilts the laser beam irradiation unit in the direction of the tilt angle predicted by the prediction unit.

  The control method according to the present invention includes a laser beam irradiating unit that irradiates an optical disc with laser light, a tilt angle changing unit that changes a tilt angle of the laser beam irradiating unit with respect to the optical disc, and a control value obtained from the reflected light of the optical disc. A control method of the optical disk device comprising control means for controlling the tilt angle changing means so that is an extreme value, wherein the control means calculates a tilt angle of one or more locations of the optical disk; A predicting step of predicting the direction of the tilt angle at an arbitrary position of the optical disk based on the tilt angle calculated in the tilt angle calculating step, and a step of tilting the laser light irradiation unit in the direction of the tilt angle predicted by the predicting unit And have.

  According to the optical disc apparatus of the present invention, the direction of the tilt angle of the laser beam irradiation means with respect to the optical disc is predicted, and the laser beam irradiation device is tilted in the predicted direction to control the control value to be an extreme value. The skew control can be made efficient.

  Further, in the optical disc apparatus according to the present invention, the skew angle is adjusted based on the tracking error signal, so that the direction of the tilt angle can be predicted even if pits are not formed on the optical disc.

  Hereinafter, an optical disc apparatus to which the present invention is applied will be described with reference to the drawings. The present invention relates to skew control of an optical disc apparatus. The skew control is a control for adjusting the skew angle, which is the inclination of the optical disk and the optical pickup, so that the laser beam and the optical disk are optically parallel. The skew control is performed to suppress the aberration of the laser beam.

  The skew angle is affected by the warp of the optical disk. The warp of the optical disk occurs due to a temperature change, a change with time, a tension due to a printed matter on the disk surface, and the like. An optical disk warp is often simple in a certain direction. Therefore, the optical disk apparatus to which the present invention is applied predicts the direction of the skew angle based on the warp of the optical disk, and firstly tilts the optical pickup in the predicted direction to improve the efficiency of skew control.

  Next, the configuration of the optical disc apparatus 1 to which the present invention is applied will be described. FIG. 1 is a block diagram showing the optical disc apparatus 1. The optical disc apparatus 1 records data input from an external device such as a computer on an optical disc 2 such as a CD-R (Recordable), MD (Mini Disc; registered trademark), DVD (Digital Versatile Disk) or the like.

  The spindle motor 3 rotationally drives the optical disc 2 at a predetermined rotational speed. The laser diode built in the optical pickup 4 emits laser light. The laser light irradiates the optical disc 2 through the objective lens 4A. Further, the optical pickup 4 converts the detection result of the laser light quantity and the reception result of the return light of the laser light into current-voltage conversion and outputs the result to the head amplifier 6, the monitor amplifier 17, and the skew servo 20.

  The head amplifier 6 amplifies the light reception result of the return light output from the optical pickup 4 with a predetermined gain. The matrix circuit 7 performs a matrix operation on the output signal of the head amplifier 6 and outputs a tracking error signal TE, a focus error signal FE, a reproduction signal RF, and a wobble signal WB. The reproduction signal RF is output from the signal processing circuit 11. The signal processing circuit 11 performs signal processing on the reproduction signal RF.

  The servo circuit 8 operates the objective lens 4A of the optical pickup 4 so as to perform tracking control and focus control so that the signal levels of the tracking error signal TE and the focus error signal FE become predetermined signal levels.

  The slide servo circuit 9 drives the slide motor 10 to move the optical pickup 4 in the radial direction of the optical disc 2 to seek the optical pickup 4. The signal processing circuit 11 corrects the signal level of the wobble signal WB, extracts a carrier signal from the wobble signal WB, and outputs it. The spindle servo circuit 12 rotationally drives the spindle motor 3 so that the frequency of the carrier signal becomes a predetermined frequency.

  The address decoder 13 performs signal processing on the wobble signal WB to calculate address data on the optical disk 2 currently accessed by the head, and outputs this address data to a central processing unit (CPU) 14.

  An interface circuit (IF) 15 inputs and outputs control commands, status data, and data used for recording and reproduction with an external device. The CPU 14 controls the operation of the optical disc apparatus 1 in accordance with a control command input via the interface circuit 15. The CPU 14 controls the operation of the slide servo circuit 9 and the like in accordance with the address data input from the address decoder 13, thereby recording or reproducing data in response to a request from an external device.

  The modulation circuit 16 modulates the data input from the interface circuit 15 into a format suitable for recording on the optical disc 2 and outputs the data. The monitor amplifier 17 amplifies and outputs the light amount detection result of the laser beam output from the optical pickup 4. The automatic light quantity control circuit (APC) 18 outputs a light quantity control signal so that the output signal of the monitor amplifier 17 becomes a predetermined signal level. The driver 5 sets the light amount of the laser light output from the optical pickup 4 to a predetermined light amount based on the light amount control signal. Thereby, it is possible to irradiate a stable laser beam when reproducing the optical disc 2.

  Further, the driver 5 uses the light amount control signal output from the CPU 14 during recording on the optical disc 2 as a reference, and changes the light amount of the laser light output from the optical pickup 4 according to the output data of the modulation circuit 16 from the light amount during reproduction. Launch intermittently. This laser beam records data on the optical disc 2.

  Next, the skew servo 20 and the peripheral configuration related to the skew servo 20 will be described with reference to FIG. In the optical disc apparatus 1, the optical pickup 4 is disposed on a pickup base 4B that is a holding member. The pickup base 4 </ b> B is arranged so as to be movable in the radial direction of the optical disk 2 by engaging with the teeth of the feed screw rotated by the slide motor 10. The optical pickup 4 performs seek by driving the slide motor 10.

  The pickup base 4B rotates in the direction of arrow A with the end of the spindle motor 3 as a fulcrum P. On the side opposite to the fulcrum P, a rack that is moved up and down by the skew motor 22 is provided. The skew angle of the optical pickup 4 is displaced by the skew motor 22.

  The skew servo 20 digitizes the tracking error signal TE output from the matrix circuit 7 by an analog / digital conversion circuit (A / D) 32A, and outputs the digitized value to the CPU. The digital / analog conversion circuit (D / A) 32B converts the skew control signal output from the CPU 14 into analog. The driver 20E drives the skew motor 22 according to the skew control signal.

  The CPU 14 determines the initial swing direction of the optical pickup 4 at an arbitrary location on the disk 2. The initial swing direction is the direction in which the optical pickup 4 is initially swinged when data is recorded or reproduced. In order to determine the initial swing direction, the CPU 14 detects the skew angle at a plurality of locations, and predicts the initial swing direction at an arbitrary location on the disk 2 by complementing the skew values at the multiple locations.

  In general, it is known that warpage of the optical disk 2 is caused by temperature change, change with time, presence or absence of printed matter on the disk surface, disk material, and the like. The warp of the optical disc 2 is not complicated and does not undulate, but is often simple in a certain direction. Therefore, in this specific example, when the initial swing direction of the optical pickup 4 is determined, the skew is detected at two points on the optical disc 2, and the value between them is complemented with an appropriate function.

  A specific example of the skew angle complementing method will be described with reference to FIG. In this example, a skew angle R1 near the inner periphery of the disk and a skew angle R2 near the outer periphery of the disk are obtained, and the skew angle in the radial direction between R1 and R2 is complemented. The solid curve shown in FIG. 3 is the skew angle detected when the control is actually performed.

  The detected pit level is approximated to a quadratic curve in which the plus side and the minus side monotonically increase with respect to the bottom of the skew. Therefore, the magnitude relationship between any three points on the curve is a relatively simple relationship. That is, as the warp of the disk changes according to the position on the optical disk 2, the skew state also deviates from the best point by the skew change. Therefore, if the skew direction is detected in advance, even if the accurate change amount of the skew is not known, the skew does not move in the direction in which the skew deteriorates.

  Further, the CPU 14 generates an offset table 32C in which the skew direction calculated by the complement and the address of the optical disc 2 are associated with each other. In the example of FIG. 3, the skew directions at arbitrary positions on the disk are all positive.

  As described above, when the optical disc apparatus 1 starts skew control, the skew direction is predicted, and the optical pickup 4 is tilted in the predicted direction, thereby achieving efficient skew control. The warping direction of the optical disc 2 is predicted using a signal at the time of reading before writing data on the optical disc 2. For example, it is measured by searching for the peak of the tracking error signal being read or the return light of the reproduction signal RF.

  Next, a method for calculating the skew angle will be described. The skew angle can be calculated from the tracking error signal TE or the reproduction signal RF. When no pit is formed on the optical disc 2, the skew angle is calculated from the tracking error signal TE. When pits are already recorded and when pits are recorded, the skew angle can be calculated from the magnitude of the reproduction signal RF, jitter, and the like.

  In general, the skew angle deviation is related to the offset of the tracking error signal TE. The offset amount is related to the warp of the disk 2. The relationship between the tracking error signal TE and the offset amount E is as shown in FIG. The tracking error signal TE is a waveform passing through the origin when the skew angle error is 0 degree. The tracking error signal TE is offset in the minus direction when an error in the minus direction occurs, and is offset in the plus direction when an error in the plus direction occurs. The CPU 14 calculates the skew angle based on the offset amount E of the tracking error signal TE.

  An example of a method for calculating the skew angle from the tracking error signal TE will be described. In this method, the light beam from the laser light source is separated into one main spot and two side spots and irradiated onto the signal recording surface of the optical disc 2, and each of the main spot and the two side spots reflected from the signal recording surface. The reflected light flux corresponding to the above is detected, and the gain is adjusted so that the output signal levels of the divided light receiving elements that receive the reflected light flux are substantially the same for each reflected light flux.

  When tracking servo is performed along the wobble groove of the optical disk 2, the reflected light beam corresponding to the gain-adjusted main spot is received to detect the main wobble signal, and the reflected light beam corresponding to each side spot whose gain has been adjusted. The side wobble signal output for each side spot is detected, and the main wobble signal and the side wobble signal are delayed so that the timings when they are compared with each other are matched. The phase variation output waveform is generated by comparing the phases of the main wobble signal and the side wobble signal whose timings coincide with each other by delay, and the filtered phase variation waveform that passes only the signal in the predetermined band of the phase variation output waveform. Detect the amplitude of. At this time, it is possible to detect the skew by generating a skew signal including the tilt direction and the tilt amount of the optical disc 2 by differentially calculating the amplitude value of the phase fluctuation amount of both side spots.

  The skew servo 20 performs skew control. The skew control is feedback control in which the skew angle is changed in the plus direction or the minus direction so that the reproduced signal RF being recorded is minimized (the reproduced signal RF being reproduced is controlled to be maximized). By this feedback control, the skew angle of the optical pickup 4 follows an ideal value. In which direction the optical pickup 4 is inclined when skew control is started is determined based on the predicted direction of the skew angle recorded in the offset table 32C. The CPU 14 searches the offset table 32C for the prediction direction of the skew angle corresponding to the address input from the address decoder 13.

  Next, the operation of the above-described optical disc apparatus 1 will be described with reference to the flowchart of FIG. The optical disc apparatus 1 first moves the optical pickup 4 to the inner circumference side of the optical disc 2 and detects the skew angle R1 near the inner circumference of the optical disc 2 (step S11). Next, the optical disc apparatus 1 moves the optical pickup 4 to the outer peripheral side of the optical disc 2 and detects a skew angle R2 near the outer periphery of the optical disc 2 (step S12). Next, the optical disc apparatus 1 connects the skew angle R1 and the skew angle R2 with a straight line, and complements the skew angle between the inner periphery and the outer periphery. The optical disc apparatus 1 records the skew angle direction calculated by the complementation in the offset table 32C (step S13).

  When accessing a predetermined address of the optical disc 2, the optical disc apparatus 1 refers to the offset table 32C and searches for the direction of the skew angle near the accessed address. Then, skew control is started by tilting the optical pickup 4 in the direction recorded in the offset table 32C (step S14). Next, the optical disc apparatus 1 starts data recording (step S15). When starting to write data, the optical disc apparatus 1 uses the reproduction signal RF being recorded as a control amount for skew control instead of the tracking error signal TE (step S16). For a disc on which pits are formed, the skew angle can be calculated using the peak of the return light of the reproduction signal RF being reproduced.

  Here, a skew control method using the reproduction signal RF being recorded as a control amount will be described. The signal level of the reproduction signal RF decreases at the pits and increases at the lands. This is the same when data is recorded, and the signal level of the reproduced RF signal in the formed pit is lowered. More specifically, referring to FIG. 6, when the light amount of the laser beam is increased from the light amount LR at the time of reproduction to the light amount LW at the time of writing, the temperature of the information recording surface of the optical disc 2 gradually increases, When the temperature rises abnormally, the formation of the pit P is started. At this time, the reproduction signal RF is generated from the information recording surface before the pit formation until the start of pit formation, and is a ratio of the light amount at the time of recording to the light amount at the time of reproduction. As a result, the signal level rises to a large signal level VP. When the temperature of the information recording surface is sufficiently increased and the formation of pits is started, the return light amount of the reproduction signal RF is rapidly reduced. When the signal level VL of the reproduction signal RF is reached, the signal level decrease stops.

  The signal level VL is the amount of return light when the pit being formed is irradiated. When the pits are irradiated at the correct angle, the amount of return light decreases, so it can be said that the lower the signal level VL, the better the control of the skew angle. The CPU 14 controls the skew angle so that the signal level VL is minimized.

  The relationship between the signal level VL and the skew angle is as shown in FIG. The signal level VP becomes minimum at the skew angle θ2, and increases monotonously regardless of whether the skew angle is changed to the plus side or the skew angle is changed to the minus side. Further, since the signal level VL is symmetrical with respect to θ2, the signal level VL is equal if the shift amount ψ is the same as shown in FIGS. 7B and 7C.

  Therefore, in the skew control, in order to detect the shift in the plus direction or the shift in the minus direction, the skew angle is changed to both the minus side and the plus side, and the control is performed in the direction in which the signal level VL decreases.

  FIG. 8 is a flowchart showing a skew control procedure using the reproduction signal RF during recording as a control amount. The CPU 14 inputs the current signal level VL1 (step S21). Then, the signal level VL2 when the skew angle is changed in the plus direction is input (step S22), and the signal level VL1 is compared with the signal level VL2. As a result of the comparison, when the signal level VL2 is lower than the previously detected signal level VL1 (step S23; YES), the skew angle is changed in the plus direction (step S24). On the other hand, when the signal level VL2 when changed in the plus direction is higher than the signal level VL1 detected previously (step S23; NO), the skew angle is changed in the minus direction (step S24). Here, when the predicted swing direction is different from the actual swing direction, the CPU 14 updates the offset database 32C (step S25).

  When continuing the writing process (step S26; NO), the CPU 14 shifts the process to step S21, and when ending the writing process (step S26; YES), ends the skew control.

  In the skew control shown in FIG. 8, the skew angle is first changed in the positive direction, but the skew angle may be changed in the negative direction first. When the signal level VL1 ′ detected first is larger than the signal level VL2 ′ detected later when the signal level is changed in the minus direction, the skew angle is changed in the minus direction so that the signal level VL1 ′ is smaller than the signal level VL2 ′. Sometimes, a process of changing the skew angle in the positive direction is performed.

  As described above, the optical disk apparatus 1 to which the present invention is applied predicts the direction of the skew angle, and creates the offset table 32C in which the skew angle direction and the address of the optical disk 2 are associated with each other. When the skew control is started, the optical pickup 4 is tilted in the direction of the predicted skew angle.

  In the present invention, since skew control is performed by predicting the direction of the skew angle, it is possible to quickly follow the ideal skew angle, and the skew control becomes efficient. Further, for skew control, even if the skew angle is changed, the difference from the ideal skew angle is not excessively widened, and the aberration caused by the skew angle deviation can be suppressed to the allowable aberration.

  On the other hand, in order to more accurately correct the skew angle, there is a complementing method that takes into consideration the characteristics depending on the manufacturer and type of the optical disc 2. The manufacturer and type of the optical disc 2 can be determined from the media ID recorded on the inner periphery of the optical disc 2.

  Further, the tracking error signal TE is a signal detected regardless of whether or not pits have already been recorded on the optical disc 2. In the optical disc apparatus 1 to which the present invention is applied, the direction of the skew angle of the optical disc 2 on which nothing is written can be predicted by using the tracking error signal TE as a control amount for skew control.

  Further, as shown in step S25 of FIG. 8, since the offset database 32C is updated with the actual skew angle, the reliability of the offset database 32C is improved every time the disk is accessed.

It is a block diagram which shows the structure of an optical disk device. It is a block diagram which shows the structure of a skew control system. It is a figure which shows the relationship between a trekking error signal and an offset amount. It is a figure which shows an example of the offset voltage prediction method. 3 is a flowchart showing the operation of the optical disc apparatus. It is a figure which shows the relationship between the laser intensity at the time of pit formation, and the reproduction signal RF. It is a figure which shows the relationship between the signal level VP and the deviation | shift of a skew angle. It is a flowchart which shows the procedure of the skew control when the reproduction signal RF is used as the control amount.

Explanation of symbols

1 optical disk device, 2 optical disk, 4 optical pickup, 7 matrix circuit, 8 servo, 13 address decoder, 14 CPU, 20 skew servo, 22 skew motor, 32A A / D circuit, 32B D / A circuit, 32C offset table

Claims (6)

Laser light irradiation means for irradiating the optical disk with laser light;
An inclination angle changing means for changing an inclination angle of the laser beam irradiation means with respect to the optical disc;
The control means for controlling the tilt angle changing means so that the control value obtained from the reflected light of the optical disk becomes an extreme value, and an arbitrary optical disc based on the tilt angle of the laser light irradiation means at one or more locations of the optical disc. And a predicting means for predicting the direction of the inclination angle at
The optical disc apparatus characterized in that the control means tilts the laser light irradiation means in a direction of an inclination angle predicted by the prediction means.   2. The optical disk according to claim 1, wherein the predicting means predicts a direction of an inclination angle at an arbitrary position from a skew angle detected at two points of an inner peripheral side and an outer peripheral side of the optical disk. apparatus.   2. The optical disk apparatus according to claim 1, further comprising predicted value storage means for storing the direction of the tilt angle calculated by the prediction means in association with an address on the optical disk.   2. The optical disk apparatus according to claim 1, wherein the predicting unit obtains an inclination angle of the laser light source irradiation unit based on a tracking error signal.   2. The optical disk apparatus according to claim 1, wherein the predicting unit obtains an inclination angle of the laser light source irradiation unit based on a reproduction signal. The laser beam irradiating means for irradiating the optical disk with laser light, the tilt angle changing means for changing the tilt angle of the laser light irradiating means with respect to the optical disc, and the control value obtained from the reflected light of the optical disc is an extreme value. A control method of an optical disc apparatus comprising control means for controlling the tilt angle changing means,
An inclination angle calculating step in which the control means calculates an inclination angle of one or more locations of the optical disc;
A prediction step of predicting the direction of the tilt angle at an arbitrary position of the optical disc based on the tilt angle calculated in the tilt angle calculating step;
And a step of tilting the laser beam irradiation means in the direction of the tilt angle predicted by the prediction means.

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