JP2007012229A - Optical disk apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an optical disk apparatus which maintains a vibration suppressing effect during seeking and invariably achieves stable access by reducing influence of a variation in sensitivity of a lens position detector which detects a position of an objective lens which normally converges and emits a light beam onto an optical disk during reproduction or recording. <P>SOLUTION: When offset characteristics are corrected during seeking or offset characteristics are corrected, a detected/updated correction value is held during high-speed movement and a drive signal for driving a tracking control actuator is output through a terminal 101c, based on an output signal of the lens position detector input to a terminal 101a upon tracking-on and a low-band signal of a tracking control signal input to a terminal 101b. A correction value hos_gain depending on a ratio of a change amount of a level of the output signal of the lens position detector to a change amount of a level of the tracking control signal is set in a multiplying means D, and a correction value center_ofs depending on a difference in level between both the input signals is set in a subtracting means H. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to an optical disc apparatus, and more particularly to an optical disc apparatus provided with a lens position detection sensor for detecting the position of an objective lens that focuses and irradiates a light beam on the optical disc.

  In a conventional optical disk apparatus, when seeking the optical head to be moved to a target track on the optical disk at high speed, the entire optical head is moved in the direction of the target track, and only the tracking control actuator is used in the vicinity of the target track. The lens is moved to the target track. However, if the moving distance of the objective lens is large, the deviation between the optical axis of the light beam and the center of the objective lens becomes large and affects the tracking control signal. It is known that an objective lens movement amount detection device for detecting the movement amount of the lens is provided, and when the movement amount of the objective lens exceeds a certain value, the optical head is stepped in a direction to return to the neutral position.

  Conventionally, when the moving mechanism of the optical head is operated to perform a high-speed search access operation, the output detection signal of the detecting means for detecting the moving amount of the condensing lens (objective lens) in the optical head in the disk radial direction is used as a feedback signal. There is known an optical disc apparatus that supplies and controls an objective lens to a lens optical axis driving mechanism that drives the objective lens in a radial direction of the optical disc in a plane perpendicular to the optical axis (see, for example, Patent Document 1). In the optical disk device described in Patent Document 1, as the detection means, for example, a dedicated sensor that detects displacement from the center of the optical axis of the objective lens from changes in the light amount, capacitance, magnetic resistance, eddy current, and the like. Using these signals, feedback control is performed on the deviation of the objective lens from the optical axis center to drive the tracking control actuator to suppress the objective lens vibration and shorten the access time. ing.

  However, in the objective lens movement amount detection device in the conventional optical disk device described above, an offset occurs even when the objective lens is in a neutral position due to the accuracy of the detection element used therein, and the movement amount and output value of the objective lens are The slope of the proportional relationship will change, and it will be necessary to adjust it for each product on which it is installed.

  Therefore, in order to solve the above problem, after storing the track position information in a state where the objective lens is in the neutral position with the tracking servo on, the tracking servo is turned off after tracking jumping by a predetermined track in the disk outer peripheral direction. On, the track position information at that time is stored, the track jumps to the inner circumference direction of the predetermined track disk, and the same is performed, and the movement amount is converted based on the stored track position information, and this and the objective at that time are recorded. 2. Description of the Related Art Conventionally, there has been known an optical disc apparatus in which a lens position detector output is corrected by matching a lens position detector output level of a lens (see, for example, Patent Document 2).

JP 58-26331 A Japanese Patent Laid-Open No. 9-212874

  However, in the conventional optical disk apparatus described in Patent Document 2, sensitivity varies depending on the temperature depending on the lens position detector. Therefore, even if the above correction operation is performed when the disk is mounted, normal playback or recording is in progress. When there is a temperature change, the gain and offset of the lens position detector fluctuate, which causes a problem of causing a reduction in vibration suppression effect during seek.

  The present invention has been made in view of the above points, and reduces the influence of fluctuations in the sensitivity of a lens position detector that detects the position of an objective lens that focuses and irradiates a light beam on an optical disk during normal playback or recording. An object of the present invention is to provide an optical disc apparatus that maintains the vibration suppressing effect during seek and can always be accessed stably.

In order to achieve the above object, the present invention provides a light source, an objective lens for focusing and irradiating a light beam emitted from the light source on the optical disc, and transmitting reflected light from the optical disc, and a reflection passing through the objective lens. An optical head including at least a photodetector that receives light and obtains an electrical signal, a head moving mechanism that moves the optical head in the radial direction of the optical disc, and a signal track on the optical disc based on the electrical signal from the photodetector Tracking error signal generating means for generating a tracking error signal according to the deviation amount of the light beam and tracking for controlling the objective lens position so that the signal track on the optical disk follows the light beam according to the tracking error signal In an optical disc apparatus comprising at least a control actuator,
The lens position detecting means for detecting the moving position of the objective lens in the radial direction of the optical disk, and the tracking position is changed in relation to the tracking error signal when the tracking control actuator is controlled according to the tracking error signal. Gain characteristic correction means for receiving the first signal and a second signal, which is a movement position detection signal of the objective lens obtained by the lens position detection means, as inputs, and sequentially detecting and correcting the gain characteristics of the lens position detection means And the offset characteristic correcting means for sequentially detecting and correcting the offset characteristic of the lens position detecting means, and the tracking control actuator is not controlled by the tracking error signal. In the tracking off state, the head moving mechanism Control means for holding the first and / or second correction values immediately before the start of high-speed movement of the gain characteristic correction means and / or the offset correction means in the signal processing means during the high-speed movement period in which the disk moves at high speed in the radial direction. And the gain characteristic correction means has a first correction value for correcting the second signal in accordance with a ratio of the amount of change in the level of the second signal to the amount of change in the level of the first signal. The offset characteristic correction unit is a unit that sets a second correction value for correcting the second signal in accordance with a difference between the level of the first signal and the level of the second signal. It is characterized by being.

  In the present invention, the level of the second signal that is the detection position of the objective lens relative to the amount of change in the level of the first signal that changes in relation to the tracking error signal such as the tracking error signal when the tracking is on. Gain characteristic correction means for setting a first correction value for correcting the second signal in accordance with the ratio of the amount of change in accordance with the difference between the level of the first signal and the level of the second signal One or both of the offset characteristic correction means for setting the second correction value for correcting the second signal is provided, and the first correction value and / or the second correction value immediately before the start of the high-speed movement is obtained. Hold and perform high-speed movement with tracking off.

  According to the present invention, the gain characteristic correction unit and the offset characteristic correction unit are provided in the tracking on state, thereby reducing the influence of the sensitivity variation of the lens position detection unit, and in the tracking on state during the high-speed movement period. Since the first correction value for gain characteristic correction and / or the second correction value for offset characteristic correction obtained at this time are held immediately before high-speed movement of the optical head performed with tracking off, tracking is performed. By switching from the on state to the high speed movement state and switching to the tracking on state again in the vicinity of the target track, it is possible to maintain the vibration suppressing effect during seek and stable access can be performed at any time.

  Next, embodiments of the present invention will be described with reference to the drawings. FIG. 1 is a block diagram showing the main part of an embodiment of an optical disk apparatus according to the present invention. In the figure, an optical head 1 includes a semiconductor laser 2, a half mirror 3, an objective lens 4, a focus control actuator 5, a tracking control actuator 6, a photodetector 7, and a lens position detector 8. The head moving mechanism 9 can move the optical disk 12 in the radial direction (indicated by a bidirectional arrow 13).

  The head moving mechanism 9 includes a pulse motor, a conversion mechanism that converts the motor shaft rotational motion of the pulse motor into a linear motion, a transmission mechanism that transmits the linear motion of the conversion mechanism to the optical head 1, and the like. A control unit 10 and an A / D converter 11 are provided outside the optical head 1, and the rotation operation of the pulse motor of the head moving mechanism 9 is controlled by the output signal of the control unit 10. In other words, the control unit 10 controls the moving operation (moving / stopping, moving speed, moving direction, etc.) of the optical head 1 via the head moving mechanism 9.

  The operation of the optical head 1 will be described. Laser light emitted from the semiconductor laser 2 is reflected by the half mirror 3 and converged on the optical disk 12 by the objective lens 4. The converged laser beam is reflected by the optical disk 12 and passes again through the objective lens 4 to the half mirror 3. The reflected light that has passed through the half mirror 3 is converged on the photodetector 7 where it is photoelectrically converted.

  The photodetector 7 is generally composed of a plurality of light receiving sections, and a read signal from the optical disk 12 obtained by photoelectric conversion separately by the plurality of light receiving sections is supplied to the control section 10 and is known here. The focus control signal FE and the tracking control signal TE are generated based on the above calculation formula, and a reproduction signal is obtained. The focus control signal FE generated by the control unit 10 is supplied to the focus control actuator 5, and the tracking control signal TE is supplied to the tracking control actuator 6.

  The focus control actuator 5 is such that the focal position of the laser light applied to the optical disc 12 is on the signal surface of the optical disc 12, and the tracking control actuator 6 is that the laser light on the signal surface of the optical disc 12 is on the optical disc 12. The objective lens 4 is driven three-dimensionally based on the focus control signal FE and the tracking control signal TE so as to follow the track.

  The control unit 10 drives the pulse motor in the head moving mechanism 9 by one pulse when the light beam is in a track following state on the optical disk 12 and the tracking control signal TE exceeds a predetermined threshold value. The optical head 1 is moved in a predetermined direction by a predetermined distance in the 12 radial directions, thereby controlling the light beam to always follow the track.

  The lens position detector 8 is a device that detects the relative movement amount of the objective lens 4 and is configured as shown in FIG. 2, for example. In FIG. 2, the lens position detector 8 holds the movable table 80, the light emitting means 82 and the light detection means 83 attached to the support column 81 fixed on the movable table 80, and the side surface of the objective lens 4. The lens holding portion 84 having a reflection surface parallel to the optical axis of the objective lens 4 on the outer side surface, the holder 85 fixed to the movable base 80, and the holder 85 and the holding portion 84 are elastically supported. And a leaf spring 86.

  Since the movable base 80 is moved integrally with the optical head 1 by the head moving mechanism 9, the light emitting means 82 and the light detecting means 83 also move integrally with the optical head 1. On the other hand, the objective lens 4 is configured to move together with the movable table 80 and to be movable in the disk radial direction by a leaf spring 86 independently of the movement of the movable table 80. The leaf spring 86 constitutes a part of the tracking control actuator 6. An optical system for irradiating a signal surface of the optical disk 12 with a light beam through the objective lens 4 and a light receiving optical system for the reflected light reflected by the optical disk 12 and incident through the objective lens 4 are shown in the lens position. Since there is no direct relationship with the detector 8, it is omitted.

  In the lens position detector 8, the light emitted from the light emitting means 82 in the direction of the objective lens 4 is reflected by the reflecting surface on the outer surface of the fixed portion 84 and received by the light detecting means 83. The light emitting means 82 always emits a substantially constant amount of light, and the light emitted from the light emitting means 82 is reflected by the reflecting surface of the fixed portion 84 having a constant reflectance. Since the objective lens 4 is three-dimensionally driven by the focus control actuator 5 and the tracking control actuator 6 independently of the movement of the movable table 80, the fixed portion 84 that moves integrally with the objective lens 4 is also movable table 80. It moves independently of movement. Therefore, the amount of light emitted from the light emitting means 82, reflected by the outer surface of the fixed portion 84 and received by the light detecting means 83 depends on the relative positions of the light emitting means 82, the light detecting means 83, and the objective lens 4. Change.

  FIG. 3 shows the relationship between the relative position between the objective lens 4 and the lens position detector 8 and the amount of light received by the light detection means 83 at this time. As shown in FIG. 3, when the objective lens 4 approaches the light emitting means 82 and the light detecting means 83 of the lens position detector 8, the amount of light received by the light detecting means 83 increases, and conversely, the objective lens 4 becomes a lens. As the distance from the light emitting means 82 and the light detecting means 83 of the position detector 8 is increased, the amount of light received by the light detecting means 83 decreases.

  Therefore, by observing the amount of reflected light from the fixed portion 84 received by the light detection means 83, the optical lens 12 is in a radial direction with respect to the movable table 80 of the objective lens 4 and on a plane parallel to the surface of the optical disk 12. The relative position can be detected. The light detection signal output from the light detection means 83 is converted into a digital signal by the A / D converter 11 in FIG. 1 and then supplied to the control unit 10.

  Next, the configuration and operation of an embodiment of the control unit 10 that forms the main part of the optical disk apparatus of the present invention will be described. FIG. 4 shows a block diagram of an embodiment of the control unit 10 in FIG. In FIG. 4, the control unit 10 receives the read signal output from the photodetector 7 as an input, and receives a focus error signal indicating a deviation amount from the focus center reference and a deviation amount from the tracking center reference by a known arithmetic expression. And a tracking error signal indicating that the lens position detection digital signal from the A / D converter 11 and the output digital signal from the A / D converter 107 are input to the input terminals 101a and 101b. A signal processing apparatus 101 (to be described later) generates a control signal for the tracking control actuator 6 and outputs it from the output terminal 101c.

  The focus error signal output from the signal generator 100 is subjected to phase compensation processing by the phase compensation circuit 102, converted to the drive signal FE by the focus driver 109, and then supplied to the focus control actuator 5 in FIG. The lens 4 is variably controlled in the direction perpendicular to the signal surface of the optical disk 12. On the other hand, when tracking is on, the tracking error signal generated by the signal generator 100 is subjected to phase compensation processing by the phase compensation circuit 103, and then supplied to the tracking driver 110 via the switch SW9 and converted to the drive signal TE. Thereafter, the objective lens 4 is supplied to the tracking control actuator 6 shown in FIG. 1 and variably controlled in the horizontal direction with respect to the signal surface of the optical disk 12 and in the radial direction of the disk.

  The tracking error signal output from the phase compensation circuit 103 is filtered by the low-pass filter (LPF) 104 to obtain a tracking error signal low-frequency component SE. The low frequency component SE is converted into a digital signal by the A / D converter 107 and then input to the input terminal 101 b of the signal processing device 101. The low frequency component SE is compared with the threshold value VSTH by the comparator 105, and the pulse generator 106 is driven and controlled based on the comparison result. The output pulse of the pulse generator 106 is applied as a drive signal to the pulse motor (step motor) in the head moving mechanism 9 of FIG.

  Also, the digital signal output from the output terminal 101c of the signal processing device 101 is converted into an analog signal by the D / A converter 108, and then passes through the switch SW9 and the tracking driver 110 except when tracking is on such as when seeking. 1 is supplied as a drive signal to the tracking control actuator 6 of FIG.

  Next, the configuration and operation of the signal processing apparatus 101 that forms the main part of the control unit 10 will be described in more detail. FIG. 5 shows a block diagram of an embodiment of the signal processing apparatus 101. In the figure, the same components as in FIG. First, the signal processing apparatus 101 shown in FIG. 5 performs offset normalization. Normalization is to correct variations in the gain and offset of the lens position detector 8 in the initial state. When the offset is normalized, the switches SW1, SW4, SW5, and SW6 in FIG. 5 are connected to the offset normalization side terminals, respectively. At the same time, the switches SW7 and SW8 are respectively connected to the normalization side terminals, and the switches SW2 and SW3 are not connected to either terminal.

  Thereby, the 0 signal output from the 0 generator 114 is supplied from the output terminal 101c to the D / A converter 108 of FIG. 4 via the switches SW6 and SW7, and after being converted into an analog signal here, It is amplified by the tracking driver 111 via the switch SW9 to be a tracking control signal TE, which is supplied to the tracking control actuator 6 in FIG. 1 to drive it. At the same time, the 0 signal output via the switch SW7 is supplied to the measuring means (F) 123 via the switch SW8, and the level is measured and then supplied to the subtracting means (G) 125. Is done.

  On the other hand, the lens position detection digital signal from the lens position detector 8 input from the A / D converter 11 via the input terminal 101a is output from the 0 generator 117 input via the switch SW1 by the adder 116. After being added to the 0 signal, the signal is supplied to the measuring means (E) 124 through the multiplier 118 and the switch SW4 that multiplies the coefficient “−1”, and is measured as the level of the signal tps. Assuming that the level of the signal tps measured by the measuring means (E) 124 is ee, the subtracting means (G) 125 subtracts the level ee from the measurement level 0 from the measuring means (F) 123 to obtain a level. The ee signal is output, supplied to the storage means 126 via the switch SW5, and stored.

  The level ee signal stored in the storage unit 126 is read from the storage unit 126 and supplied as an offset correction signal offset_v to the adder 116 via the multiplier 127 that multiplies “−1”. When added to the position detection digital signal (that is, offset_v is subtracted), the level ee first measured by the measuring means (E) 124 is canceled and becomes 0, and the offset is corrected. Thus, at the time of offset normalization, the input tracking control signal TE of the tracking control actuator 6 is set to 0, the level ee of the tps signal is measured, and offset_v is set so that it becomes 0.

  Next, gain normalization is performed. At the time of gain normalization, the switches SW1, SW4, and SW5 in FIG. 5 are connected to the terminal opposite to the offset normalization side terminal, the switches SW2, SW3, and SW6 are connected to the gain normalization side terminal, and the switch SW7 and SW8 are each connected to the normalization side.

  Thereby, the triangular wave having a specific amplitude output from the triangular wave generator 113 is supplied from the output terminal 101c to the D / A converter 108 in FIG. 4 via the switches SW6 and SW7, and is converted into an analog signal here. Thereafter, the signal is further amplified by the tracking driver 111 via the switch SW9 to be a tracking control signal TE, which is supplied to the tracking control actuator 6 in FIG. 1 to drive it. At the same time, the triangular wave output via the switch SW7 is supplied to the measuring means (B) 115 for measuring the difference (or integrated value) between the two times via the switch SW8, and the tracking control actuator. 6 is measured as a voltage fluctuation value bb for driving 6.

  On the other hand, the lens position detection digital signal by the lens position detector 8 input from the A / D converter 11 via the input terminal 101a is opposite to the offset correction signal offset_v input by the adder 116 via the switch SW1. After the offset is corrected by adding in polarity, a difference (or integration) between two times is performed via a multiplier 118 that multiplies the coefficient “−1”, a multiplier 119 that multiplies the coefficient “1”, and the switch SW2. Is supplied as a signal tps to the measuring means (A) 120 for measuring the value), and the level difference between the two times is measured. Note that the multiplier 119 is provided for waveform shaping, but is not essential and may not be provided. At this time, the measurement means (A) 120 measures the fluctuation value aa of the tps signal when the tracking control actuator 6 is driven.

  The calculation means (C) 121 is a ratio (bb / b) between the fluctuation value aa of the tps signal from the measurement means (A) 120 and the voltage fluctuation value bb for driving the tracking control actuator 6 from the measurement means (B) 115. aa) is calculated, and the calculation result (bb / aa) is set and stored in the multiplication means (W) 122 as the multiplication coefficient gain_A. As a result, the fluctuation value of the tps signal output from the multiplication means (W) 122 during normal tracking control for two times becomes bb, and the fluctuation value of the tps signal for two times and the voltage for driving the tracking control actuator 6 are obtained. The fluctuation value becomes equal, and the gain of the lens position detector 8 is normalized.

  When the above offset gain normalization and gain normalization are completed, normal thread feeding is performed during optical disc reproduction or recording, and tracking control is performed. During tracking control (when tracking is on), the switch SW8 is connected to the tracking-on-side terminal, the switches SW1, SW4, and SW5 are the opposite terminals of the offset normalization-side terminal, and the switches SW2 and SW3 are The switches SW6 and SW7 are connected to the terminals on the opposite side of the gain normalization side terminals, and are not connected to either terminal. The switch SW9 in FIG. 4 is also connected to the tracking-on side terminal.

  Thus, the low-frequency component SE of the tracking error signal filtered by the low-pass filter (LPF) 104 in FIG. 4 is converted into a digital signal by the A / D converter 107, and then the input terminal 101b and the switch in FIG. It is supplied to the measuring means (B) 115 via SW8 and the fluctuation value between two times is measured. On the other hand, the tps signal, which is a product of the multiplication coefficient gain_A of the offset-corrected lens position detection digital signal extracted from the multiplication means (W) 122, is supplied to the multiplication means (D) 128, while the switch SW ( A) It is supplied to 120 and the fluctuation value between two times is measured.

  The variation value of the measurement means (A) 120 is equal to the variation value of the measurement means (B) 115, the output signal of the calculation means (C) 121 is “1”, and this value is multiplied by the switch means via the switch SW3. (D) 128 is set and stored as a multiplication coefficient hos_gain. At this time, the output signal of the subtraction means (G) 125 is “0”, and the value center_ofs supplied to the subtraction means (H) 129 via the switch SW5 is “0”.

  Next, the operation at the time of thread feeding in FIG. 4 will be described. FIG. 6 shows signal waveforms at various parts in FIG. 4 during the thread feeding operation. The SE signal output from the LPF 104 in FIG. 4 corresponds to the low frequency component of the tracking error signal, and when the tracking servo is applied, the lens shift from the lens center position as shown in FIG. It corresponds to a signal indicating the quantity.

  The SE signal is supplied to the comparator 105, the level of which is compared with the threshold value VSTH, and when the SE signal level exceeds the threshold value VSTH, the pulse generator 106 generates a signal based on the signal from the comparator 105. One pulse SD as shown in FIG. 6 (B) is generated, and the pulse motor in the head moving mechanism 9 in FIG. 2 moves by a predetermined distance in the outer circumferential direction of the optical disc 1, whereby the center position of the objective lens 4 approaches the optical axis center, the level of the SE signal decreases, and the tps signal also decreases. The level drops. In the initial state, since it is normalized, the fluctuations of these two signals are equal.

  When the tracking is on as described above, the signal processing apparatus 101 detects the change in the gain characteristic and the offset characteristic, and applies the multiplication coefficient hos_gain set in the multiplication unit (D) 128 and the subtraction unit (H) 129. The supplied value center_ofs is updated and output.

  Next, the operation during seek will be described. When seeking to move the optical head 1 to the target track on the optical disk 12 at high speed, the tracking is switched from the tracking-on state when the current track is reproduced to the off-state, and the optical head 1 is moved to the target track at high speed. The high-speed movement to be performed and the tracking-on state in which the tracking is turned on when the optical head 1 comes near the target track and the target track is accurately scanned are repeated.

  During the high-speed movement, the pulse generator 106 generates continuous pulses, drives the pulse motor in the head moving mechanism 9 in FIG. 1, and moves the movable table 80 in FIG. 2 at high speed. At this time, the switches SW7 and SW8 in FIG. 5 are connected to the high speed movement side. Thereby, the subtraction signal tps2 between the tps signal output from the subtraction means (H) 129 and the center_ofs is added to the control reference value (constant) center_v when the lens position control is performed by the adder 130, and then the gain. A predetermined frequency component is extracted by the loop filter 131 and is output via the switch SW7 and the output terminal 101c. Further, the tracking of FIG. 1 is performed via the D / A converter 108, the switch SW9 and the tracking driver 110 of FIG. This is supplied to the control actuator 6 to drive it. By this feedback control, vibration of the objective lens 4 during high-speed movement can be suppressed.

  Next, an operation during high-speed movement when the gain characteristic of the lens position detector 8 changes will be described. In the initial state, when the lens position detector 8 has the gain characteristic indicated by x0 in FIG. 3 but has changed to the characteristic indicated by x1, the tps signal output from the multiplying means (W) 122 in FIG. In FIG. 6C, the maximum value increases from Max_x0 to Max_x1. As a result, the gain of feedback control at the time of high-speed movement is increased, and the control performance is deteriorated or oscillation is likely to occur.

  However, in this embodiment, the measuring means (A) 120 shown in FIG. 5 measures the level difference between the time t1 and the time t2 of the tps signal shown in FIG. 6C, and (b3-b1) in the initial state. ) After the characteristic change, the value of (b4-b1) is obtained (however, the level at point B1 in FIG. 6C is b1, the level at point B3 is b3, and the level at point B4 is b4).

  On the other hand, the SE signal, which is the low frequency component of the tracking error signal, is converted into a digital signal by the A / D converter 107 immediately before the high-speed movement, and then passes through the switch SW8 connected to the tracking-on side. The level difference (or integrated value) measuring means (B) 115 between two times is supplied to measure the level difference between the two times, and the measurement signal is supplied to the calculating means (C) 121. Here, the SE signal is shown in FIG. 6A. At time t1, the signal level a1 at the point A1 is obtained at both the initial state and after the characteristic change, and at time t2, the initial state and after the characteristic change. Each of these is the signal level a3 at the point A3. Therefore, the measuring means (B) 115 obtains the value of (a3-a1) both in the initial state and after the characteristic change in the tracking-on state immediately before the high-speed movement.

  On the other hand, in the initial state, the measurement result of the measurement means (A) 120 is (b3-b1) and the measurement result of the measurement means (B) 115 is (a3-a1). In the state, the ratio of (a3-a1) / (b3-b1) is obtained. After the characteristic change, the measurement result of the measuring means (A) 120 is (b4-b1), and the measurement result of the measuring means (B) 115 is Since (a3-a1), the calculation means (C) 121 obtains the ratio of (a3-a1) / (b4-b1) in the state after the characteristic change, and this value is multiplied by the multiplication means ( D) Set to 128 as a multiplication coefficient (gain) hos_gain.

  The multiplication coefficient (gain) hos_gain (= (a3−a1) / (b3−b1)) of the calculation means (D) 128 is “1” in the initial state as described above, and the gain of the lens position detector 8 The increase in the amplitude of the tps signal due to the characteristic change is canceled by multiplying the tps signal by this hos_gain, and the multiplication output signal is subtracted from the center_ofs by the subtracting means 129 and the tps2 as shown in FIG. Signal.

  The tps2 signal is added to the reference value center_v in the adder 130, and then a predetermined frequency component is extracted by the gain loop filter 131 and output via the switch SW7 and the output terminal 101c. 1 is supplied to the tracking control actuator 6 of FIG. 1 through the A converter 108, the switch SW9 and the tracking driver 110 to drive it.

  Here, during high-speed movement, the switch SW8 is connected to the high-speed movement side terminal, and the detection and updating of the hos_gain and center_ofs are not performed, and the measurement values of the measurement units 123 and 124 and the multiplication unit 128 are set. “Hos_gain” and “center_ofs” set in the subtracting means 129 hold the values at the time of tracking-on immediately before the high-speed movement, respectively. Thereby, even when the gain characteristic of the lens position detector 8 is changed, the gain of the tracking feedback control at the time of high-speed movement does not change, so that the control performance is not deteriorated.

  In the above description, the difference between two times of a signal is used as a value, but this may be an integrated value between two times. In this case, the value of the measuring means (A) 120 is the area of the triangle B1B3B2 shown in FIG. 6C in the initial state, and the area of the triangle B1B4B2 after the characteristic change. The value of the measuring means (B) 115 is the area of the triangle A1A3A2 shown in FIG. 6A in the initial state and the area of the triangle A1A3A2 even after the characteristics change. In the calculation means (C) 121, in the initial state (the area of the triangle A1A3A2) / (the area of the triangle B1B3B2) (this value is 1 as described above), after the characteristic change, (the area of the triangle A1A3A2) / (triangle The value of (area of B1B4B2) is obtained, and it is understood that this is the same as the value of (a3-a1) / (b3-b1) and (a3-a1) / (b4-b1) described above. The advantage of using the integrated value is that a large amount of data is captured, so that the influence of noise is reduced.

  Next, an operation when the offset characteristic of the lens position detector 8 changes during high-speed movement of the optical head 1 will be described. In this case, when the lens position control is performed, the control is performed in a state where the lens position of the objective lens 4 is deviated, so that a controllable range (dynamic range) is narrowed. In addition, since control is performed in a state where the lens position of the objective lens 4 is shifted, there is a problem that power consumption during control increases.

  FIG. 7 is a characteristic diagram of an example when an offset occurs in the lens position detector 8. In this case, when an offset occurs with respect to the characteristic x0 when the relative light quantity of the received light amount of the light detection means 83 shown in FIG. 2 and the objective lens 4 is normal in FIG. 7, for example, the offset characteristic becomes x0. It changes like x2 represented by a parallel straight line.

  When the offset characteristic changes to the characteristic indicated by x2, the tps signal output from the multiplying means (D) 128 causes an offset in the + direction as shown in FIG. 8C, and the maximum amplitude level changes to Max_x2. 8A shows an SE signal which is a low frequency component of the tracking error signal output from the LPF 104 shown in FIG. 4, and FIG. 8B shows an output signal of the pulse generator 106 shown in FIG. SD is shown.

  In the signal processing apparatus 101 shown in FIG. 5, in the tracking-on state immediately before high-speed movement, the measuring means (E) 124 receives the tps signal shown in FIG. 8C as an input, and measures the level tps1 of the tps signal at time t3. On the other hand, the measuring means (F) 123 receives the SE signal shown in FIG. 8A as an input, and measures the level se1 of the SE signal at time t3. The subtraction means (G) 125 of FIG. 7 subtracts the measurement value of the measurement means (E) 124 and the measurement value of the measurement means (F) 123 at the same time t3 to calculate the subtraction result of (tps1-se1). Then, this is supplied to the subtraction means (H) 129 and set as an offset value center_ofs.

  The subtracting means (H) 129 subtracts the offset value center_ofs from the tps signal corresponding to the output signal of the lens position detector 8 to thereby remove the offset tps2 signal as shown in FIG. 8D. Is supplied to the adder 130.

  Subsequently, high-speed movement to the target track is started. Here, as described above, during the high-speed movement, the switches SW7 and SW8 are connected to the high-speed movement side terminal, and the detection and updating of the hos_gain and the center_ofs are not performed, and the measurement of each of the measurement units 123 and 124 is performed. The value, hos_gain set in the multiplying unit 128, and center_ofs set in the subtracting unit 129 hold the values at the time of tracking-on immediately before the high-speed movement, respectively.

  As a result, when the high-speed movement of the lens position detector 8 is started, the subtraction means (H) 129 holds the offset value center_ofs set immediately before the high-speed movement during the high-speed movement period, so that the lens position detector By subtracting the offset value center_ofs from the tps signal corresponding to the output signal of 8, the tps2 signal from which the offset is removed is output and supplied to the adder 130.

  The adder 130 supplies a signal obtained by adding the tps2 signal and the reference value center_v to the gain loop filter 131 to select a frequency of a predetermined frequency component. The output signal of the in-loop filter 131 is output via the switch SW7 and the output terminal 101c, and further via the D / A converter 108, the switch SW9 and the tracking driver 110 of FIG. 6 to drive it. In this way, the offset when the offset characteristic of the lens position detector 8 changes can be removed during high-speed movement. Thus, according to the present embodiment, both the gain and offset of the lens position detector 8 can be corrected.

  The present invention is not limited to the above-described embodiment. For example, in the above-described embodiment, the signal processing apparatus 101 detects a gain characteristic of the lens position detector 8 and corrects the gain characteristic correction unit ( The offset characteristic correcting means for detecting and correcting the offset characteristic of the lens position detector 8 at the subsequent stage of the measuring means (A) 120, the measuring means (B) 115, the calculating means (C) 121, and the multiplying means (D) 128). (Measuring means (E) 124, measuring means (F) 123, subtracting means (G) 125, and subtracting means (H) 129) are connected, but the order of connection may be the reverse of the embodiment, and the gain Although both the characteristic correction means and the offset characteristic correction means are provided, only one of them may be provided.

  Further, in the above embodiment, the gain and offset are corrected using the SE signal which is the low frequency component of the input signal of the tracking driver 110. This is because the objective lens This is because the signal is proportional to the lens movement amount of 4, and any other signal can be used as long as it is such a signal. Therefore, a signal generated based on the tracking control signal or tracking error signal in FIG. Alternatively, a signal obtained by reading these signals a predetermined number of times and averaging the data may be used.

1 is a block diagram of an embodiment of an optical disk device of the present invention. It is a block diagram of one Embodiment of the lens position detector in FIG. It is a characteristic view of an example of the lens position detector in FIG. It is a block diagram of one Embodiment of the control part in FIG. It is a block diagram of one Embodiment of the signal processing apparatus in FIG. 5 is a timing chart at the time of normal thread feeding in FIG. 4. It is a characteristic view of the other example of the lens position detector in FIG. It is a timing chart at the time of normal thread feeding of FIG.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Optical head 2 Semiconductor laser 3 Half mirror 4 Objective lens 5 Actuator for focus control 6 Actuator for tracking control 7 Optical detector 8 Lens position detector 9 Head moving mechanism 10 Control part 11 A / D converter 12 Optical disk 80 Movable stand 82 Light emitting means 83 Light detecting means 84 Lens holding part 86 Leaf spring 100 Signal preparation part 104 Low-pass filter (LPF)
105 Comparator 106 Pulse generator 109 Focus driver 110 Tracking driver 111 Step driver 115, 120 Two-time difference (or integrated value) measuring means 121 Arithmetic means 122, 128 Multiplier means 123, 124 Level measuring means 125, 129 Subtracting means 126 storage means SW1 to SW9 switch

Claims (1)

A light source, a light beam emitted from the light source is focused on the optical disc, and an objective lens that transmits the reflected light from the optical disc, and the reflected light that passes through the objective lens is received to obtain an electrical signal. An optical head including at least a photodetector;
A head moving mechanism for moving the optical head in the radial direction of the optical disc;
Tracking error signal generating means for generating a tracking error signal according to the amount of deviation between the signal track on the optical disc and the light beam based on the electrical signal from the photodetector;
In an optical disc apparatus comprising at least a tracking control actuator for controlling the position of the objective lens so that a signal track on the optical disc follows the light beam according to the tracking error signal,
Lens position detecting means for detecting the moving position of the objective lens in the radial direction of the optical disc;
The first signal that changes in relation to the tracking error signal and the objective obtained by the lens position detection means when the tracking control actuator is controlling the tracking control actuator according to the tracking error signal. A second characteristic signal, which is a lens movement position detection signal, is received as an input, and a gain characteristic correction unit that sequentially detects and corrects the gain characteristic of the lens position detection unit, and an offset characteristic of the lens position detection unit is sequentially detected. And signal processing means comprising either or both of the offset characteristic correction means for correcting,
In the tracking-off state in which the tracking control actuator is not controlled by the tracking error signal, during the high-speed movement period in which the optical head is moved in the radial direction of the optical disk by the head moving mechanism, Control means for holding the first and / or second correction values immediately before the start of the high speed movement of the gain characteristic correction means and / or the offset correction means, and the gain characteristic correction means includes the first characteristic correction means. Means for setting the first correction value for correcting the second signal in accordance with a ratio of the amount of change in the level of the second signal to the amount of change in the level of the signal; The second correction for correcting the second signal according to the difference between the level of the first signal and the level of the second signal An optical disc apparatus characterized by being means for setting a value.

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