JP2009163786A - Optical disk drive and tracking control method thereof - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an optical disk drive and a tracking control method which maintains high precision tracking control even when the phase of a side beam changes against a main beam due to environmental temperature change and the recording or reproducing positions on the optical disk. <P>SOLUTION: This optical disk drive has subtractors 113, 114 to generate first and second tracking error signals from the main beam and the side beam separated from the emitted light, a low-pass filter 120 to pass a predetermined frequency or lower of the second tracking error signals to obtain a third tracking error signals, and a CPU119 to subtract the second tracking error signals from the first tracking error signals to generate tracking error signals. When the tracking error signals do not exceed a predetermined amplitude, the CPU119 generates the tracking error signals by using the third tracking error signals instead of the second tracking error signals. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to an optical disc apparatus that performs at least one of recording and reproduction of information on an optical disc and a tracking control method thereof.

  When recording information on an optical disk or reproducing information recorded on an optical disk, it is necessary to focus light emitted from a light source on a predetermined track on the recording surface of the optical disk. A condensing lens called an objective lens is usually used for this condensing, and tracking control is performed to move the objective lens in the tracking direction so that the light emitted from the objective lens reaches the target track. The light emitted from the light source can be optimally condensed on the recording surface of the optical disc. The tracking control is performed using a tracking error signal “TE” generated based on the reflected light from the optical disk.

  The light emitted from the optical disk is split into one main beam and two sub beams to generate a main beam tracking error signal “MTE” from one main beam, and a sub beam tracking error signal “STE” from the two sub beams. Generate. Thereafter, the sub beam tracking error signal “STE” is subtracted from the main beam tracking error signal “MTE” to generate a tracking error signal “TE”.

“TE” = “MTE” − “STE” (Formula 1)
Here, since “MTE” is normally a sine wave and “STE” is a sine wave having an opposite phase to “MTE”, it can be defined as follows.

“MTE” = Asin θ (Formula 2)
“STE” = − Asin θ (Formula 3)
Therefore, the tracking error signal “TE”
“TE” = “MTE” − “STE” = 2 Asin θ (Formula 4)
Thus, tracking control is performed using this 2A sin θ.
JP 2002-304753 A

However, the temperature of the environment in which the optical disk apparatus is used changes, and the phase of the sub beam tracking error signal “STE” changes due to the temperature change, and is shifted by 180 ° with respect to the main beam tracking error signal “MTE”. In some cases, the phase was substantially the same as the main beam tracking error signal “MTE”. In this case, since “STE” becomes Asinθ, the tracking error signal “TE”
“TE” = “MTE” − “STE” ≈0 (Formula 5)
As a result, the tracking error signal “TE” becomes too small to function as a tracking error signal, which causes a problem in tracking control of the objective lens.

  The present invention has been made to solve the above-described problems, and an object thereof is to provide an optical disc apparatus and a tracking control method thereof that always maintain highly accurate tracking control even when the temperature of the usage environment changes. And

  The present invention has been made to solve the above-described problems, and includes a light source, a spectroscopic unit that splits light emitted from the light source into a main beam and a sub beam having a phase different from that of the main beam, and an optical disc. First tracking error signal generating means for generating a first tracking error signal based on the main beam reflected from the optical disk after reaching, and a second tracking error signal based on the sub beam reflected from the optical disk after reaching the optical disk A second tracking error signal generating means for performing the processing, a filter for extracting a third tracking error signal through a frequency equal to or lower than a predetermined frequency of the second tracking error signal, and a tracking by subtracting the second tracking error signal from the first tracking error signal Control means for generating an error signal, and the control means has a tracking error. No. is an optical disk apparatus characterized by generating a tracking error signal using a does not exceed the predetermined amplitude value, the third tracking error signal in place of the second tracking error signal.

  In the present invention, the light emitted from the light source is split into a main beam and a sub beam having a phase different from that of the main beam, and the first tracking error signal is generated based on the main beam reflected from the optical disc after reaching the optical disc. Generating a second tracking error signal based on the sub beam reflected from the optical disk after reaching the optical disk, passing a second tracking error signal below a predetermined frequency, extracting a third tracking error signal, When generating the tracking error signal by subtracting the second tracking error signal from the one tracking error signal, if the tracking error signal does not exceed the predetermined amplitude value, the third tracking error signal is used instead of the second tracking error signal. Tracking of an optical disk device characterized by generating a tracking error signal It is a control method.

  According to the above configuration, the tracking error signal has a constant amplitude value within a certain range since the signal used to generate the tracking error signal is used depending on whether the tracking error signal exceeds the predetermined amplitude value or not. The tracking error signal can be generated without being affected by the phase value of the sub beam with respect to the main beam. As a result, the tracking error signal is generated without being affected by the phase value of the secondary beam with respect to the main beam, so even when the temperature of the usage environment changes, high-precision tracking control is always maintained and accurate. An accessible optical disc apparatus and a tracking control method thereof can be realized.

  According to the first aspect of the present invention, there is provided a light source, a spectroscopic means for splitting light emitted from the light source into a main beam and a sub beam having a phase different from that of the main beam, and a main beam reflected from the optical disk after reaching the optical disk. First tracking error signal generating means for generating a first tracking error signal based on the second tracking error signal generating means for generating a second tracking error signal based on the secondary beam reflected from the optical disk after reaching the optical disk; A filter for passing the second tracking error signal below a predetermined frequency and extracting the third tracking error signal; and a control means for generating a tracking error signal by subtracting the second tracking error signal from the first tracking error signal; And the control means, when the tracking error signal does not exceed a predetermined amplitude value, It is characterized in that for generating a tracking error signal using a third tracking error signal in place of the second tracking error signal. This makes it possible to keep the amplitude value of the tracking error signal within a certain range because the signal used to generate the tracking error signal is used differently depending on whether the tracking error signal exceeds the specified amplitude value or not. The tracking error signal can be generated without being affected by the phase value of the sub beam with respect to the main beam. As a result, since the tracking error signal is generated without being affected by the phase value of the sub beam with respect to the main beam, an optical disc apparatus that always maintains high-precision tracking control even when the temperature of the usage environment changes. realizable.

  The invention according to claim 2 is characterized in that the control means determines that the tracking error signal exceeds a predetermined amplitude value when the phase of the first tracking error signal and the phase of the second tracking error signal are substantially the same. To do. Thus, the control means measures and compares the phase of the first tracking error signal and the phase of the second tracking error signal without actually calculating the tracking error signal from the first tracking error signal and the second tracking error signal. Since it is determined whether or not the tracking error signal exceeds a predetermined amplitude value, it is easy to use the second tracking error signal or the third tracking error signal when generating the tracking error signal. The configuration can be determined in a short time.

  According to a third aspect of the present invention, when the control means has a difference between the phase of the first tracking error signal and the phase of the second tracking error signal of 20 degrees or less, the phase of the first tracking error signal and the second tracking error signal Are determined to be substantially the same phase. Thereby, the control means does not accurately measure the phase of the first tracking error signal and the phase of the second tracking error signal, and the phase of the first tracking error signal and the phase of the second tracking error signal are substantially the same. Since it is determined whether or not there is, it can be determined with a simpler configuration and in a shorter time.

  According to a fourth aspect of the present invention, there is provided a rotation driving means for rotating the optical disc, and the filter generates the third tracking error signal by reducing the amplitude of the second tracking error signal while passing only the rotation frequency component of the optical disc. It is characterized by this. This reduces the amplitude of the tracking error signal while maintaining the frequency component required for tracking control, so when generating a tracking error signal, a third tracking error signal that can be used in place of the second tracking error signal is generated. it can.

  The invention according to claim 5 is characterized in that the predetermined frequency of the filter is switched in accordance with the rotational speed of the rotation driving means. Accordingly, since only the frequency component necessary for tracking control is maintained when generating the third tracking error signal from the second tracking error signal, highly accurate tracking control can be performed in accordance with the rotational speed of the optical disc.

  According to the sixth aspect of the present invention, the first tracking is performed based on the main beam reflected from the optical disk after reaching the optical disk after the light emitted from the light source is split into the main beam and the sub beam having a phase different from that of the main beam. Generate an error signal, generate a second tracking error signal based on the secondary beam reflected from the optical disk after reaching the optical disk, pass the second tracking error signal below a predetermined frequency, and extract the third tracking error signal When generating the tracking error signal by subtracting the second tracking error signal from the first tracking error signal, if the tracking error signal does not exceed a predetermined amplitude value, the third tracking error signal is used instead of the second tracking error signal. And a tracking error signal is generated. This makes it possible to keep the amplitude value of the tracking error signal within a certain range because the signal used to generate the tracking error signal is used differently depending on whether the tracking error signal exceeds the specified amplitude value or not. The tracking error signal can be generated without being affected by the phase value of the sub beam with respect to the main beam. As a result, since the tracking error signal is generated without being affected by the phase value of the sub beam with respect to the main beam, the phase of the sub beam with respect to the main beam changes depending on the temperature change of the use environment or the recording or reproducing position on the optical disk. Even in this case, it is possible to realize tracking control of the optical disc apparatus that always maintains highly accurate tracking control.

  The invention according to claim 7 is characterized in that when the phase of the first tracking error signal and the phase of the second tracking error signal are substantially the same, it is determined that the tracking error signal exceeds a predetermined amplitude value. . Thus, the tracking error signal can be tracked only by measuring and comparing the phase of the first tracking error signal and the phase of the second tracking error signal without actually calculating the tracking error signal from the first tracking error signal and the second tracking error signal. Since it is determined whether or not the error signal exceeds a predetermined amplitude value, it is easy to determine whether to use the second tracking error signal or the third tracking error signal when generating the tracking error signal. You can decide on time.

  According to the eighth aspect of the present invention, when the tracking error signal is generated by subtracting the second tracking error signal from the first tracking error signal, the difference between the phase of the first tracking error signal and the phase of the second tracking error signal is When the angle is 20 degrees or less, it is determined that the phase of the first tracking error signal and the phase of the second tracking error signal are substantially the same phase. Thus, whether or not the phase of the first tracking error signal and the phase of the second tracking error signal are substantially the same without accurately measuring the phase of the first tracking error signal and the phase of the second tracking error signal. Therefore, it can be determined with a simpler configuration and in a shorter time.

  According to the ninth aspect of the present invention, when the third tracking error signal is extracted by passing the second tracking error signal below the predetermined frequency, the amplitude of the second tracking error signal is adjusted while passing only the rotational frequency component of the optical disk. The third tracking error signal is generated by reducing the size. This reduces the amplitude of the tracking error signal while maintaining the frequency component required for tracking control, so when generating a tracking error signal, a third tracking error signal that can be used in place of the second tracking error signal is generated. it can.

  The invention described in claim 10 is characterized in that the predetermined frequency is substantially the same as the maximum rotation frequency of the optical disc. As a result, only the frequency component necessary for tracking control is maintained when generating the third tracking error signal from the second tracking error signal, so that high-accuracy tracking control is performed according to the maximum number of rotations of the optical disc that the optical disc apparatus can handle. Can do.

(Embodiment 1)
Embodiment 1 of the present invention will be described below with reference to the drawings.

  FIG. 1 is a block diagram of an optical disc apparatus according to Embodiment 1 of the present invention. In FIG. 1, 1 is a light source, 4 is an objective lens, 5 is an optical disk, 15 is a lens driving mechanism, 15a is a tracking adjustment coil, 119 is a CPU, 25 is a light detector, 28 is a light detector, and 45 is light detection. , 100 is a signal processing circuit, 117 is a filter, 118 is a tracking driver, 206 is a spindle motor, 207 is a feed motor, 216a is a spindle driver, 216b is a laser driver, 300 is an optical head unit, and 400 is a pickup module. In the first embodiment, the light source corresponds to the light source 1 and the rotation driving means corresponds to the spindle motor 206.

  The pickup module 400 includes a spindle motor 206 that rotates the optical disc 5, an optical head unit 300 that irradiates the optical disc 5 with light and receives reflected light from the optical disc 5, and the optical head unit 300 in the tracking direction (radial direction) of the optical disc 5. And a feed section provided with a feed motor 207 to be moved.

  The optical head unit 300 includes a light source 1 that emits light to be applied to the optical disc 5, an objective lens 4 that condenses the emitted light from the light source 1, a lens driving mechanism 15 that drives the objective lens 4, and an optical disc 5 Photodetectors 25, 28, and 45 that receive reflected light via the objective lens 4 are provided.

  The lens driving mechanism 15 is provided with a tracking adjustment coil 15a, a focus adjustment coil, a magnet (not shown), and the like. The lens driving mechanism 15 moves the objective lens 4 in the tracking direction and the focus direction by passing an electric current through the coil. Perform adjustment and focus adjustment.

  The photodetectors 25, 28 and 45 receive the reflected light from the optical disk 5, generate an electrical signal corresponding to the received light quantity, and output it to the signal processing circuit 100.

  The signal processing circuit 100 generates a tracking error signal based on the signals input from the photodetectors 25, 28, and 45, and drives the lens driving mechanism 15 via the filter 117 and tracking driver 118 using the tracking error signal. The objective lens 4 is moved to execute tracking control.

  The CPU 119 receives signals sent from the signal processing circuit 100, performs arithmetic processing on these signals, sends out the result (signal) of the arithmetic processing from the signal processing circuit 100, and processes and executes the signal processing circuit 100. To control each part.

  The spindle driver 216a, laser driver 216b, and tracking driver 118 respectively drive the spindle motor 206 to rotate the optical disk 5, adjust the light emission amount of the light source 1, and drive the lens driving mechanism 15 in accordance with instructions from the CPU 119. The tracking control of the lens 4 is performed.

  The filter 117 is a filter that causes the optical head unit 300 to follow a track on the optical disk 5 and is called a servo filter.

  FIG. 2 is a diagram showing the optical pickup device according to Embodiment 1 of the present invention. In FIG. 2, 1 is a light source, 2 is a collimator lens, 4 is an objective lens, 5 is an optical disk, 9 is a focusing lens, 15 is a lens driving mechanism, 25 is a photodetector, 28 is a photodetector, 39 is a diffraction grating, Reference numeral 40 denotes a beam splitter, 41 denotes a condensing spot, 42 denotes a condensing spot, 43 denotes a condensing spot, 45 denotes a photodetector, and 100 denotes a signal processing circuit. The spectroscopic means in the first embodiment corresponds to the diffraction grating 39.

  The light source 1 emits light that irradiates the optical disk 5, and the light emitted from the light source 1 is converted from divergent light into a parallel beam by the collimator lens 2. When the light converted into the parallel beam passes through the diffraction grating 39, it is divided into three light beams and a phase difference of about 180 degrees is given to the two light beams, and reaches the beam splitter 40. To do.

  The beam splitter 40 reflects the parallel beam from the collimator lens 2 toward the objective lens 4, and the reflected parallel beam is formed on the track surface of the optical disk 5 by the objective lens 4 as three focused spots 41, 42, 43. Information is recorded by the focused spot 41 located at the center of the three spots, or information already recorded is reproduced.

  A portion of the light that has passed through the objective lens 4 and reached the track surface of the optical disk 5 is reflected and received by the photodetectors 25, 28, and 45 via the objective lens 4, the beam splitter 40, and the focusing lens 9. The Based on the outputs of the light detectors 25, 28, 45, the lens driving mechanism 15 is driven through the signal processing circuit 100, the filter 117, and the tracking driver 118, and the objective lens 4 is moved to execute tracking control.

  FIG. 3 is a diagram showing a configuration of the focus driving device according to Embodiment 1 of the present invention. In FIG. 3, 11 is an amplifier, 15 is a lens driving mechanism, 25 is a photodetector, 28 is a photodetector, 45 is a photodetector, 48 is a light spot, 49 is a light spot, 50 is a light spot, and 101 is an amplifier. , 102 is an amplifier, 103 is an amplifier, 104 is an amplifier, 105 is an adder, 106 is an adder, 107 is an amplifier, 108 is an amplifier, 109 is an adder, 110 is an amplifier, 112 is an adder, 113 is a subtractor, Reference numeral 114 denotes a subtractor, 115 denotes an amplifier, 117 denotes a filter, 118 denotes a tracking driver, 119 denotes a CPU, 120 denotes a low-pass filter, 121 denotes a switch, and 121a, 121b, and 121c denote end portions. In the first embodiment, the control means corresponds to the CPU 119, the first tracking error signal generation means corresponds to the subtractor 113, the second tracking error signal generation means corresponds to the subtractor 114, and the filter corresponds to the low-frequency pass filter 120.

  The light detectors 25, 28, 45 use a light receiving surface divided into four parts, and the three light-converging spots 41, 42, 43 on the information recording surface are irradiated as light spots 48, 49, 50. ing.

  The output signals of the four light receiving surfaces a, b, c, d of the photodetector 25 are passed through the amplifiers 101, 102, 103, 104, and then the signals on the light receiving surface a and the signals on the light receiving surface d are added by the adder 105. This is added to become a main beam tracking error first signal (hereinafter referred to as “MTEP” signal). The signal of the light receiving surface b and the signal of the light receiving surface c are added by the adder 106 to become a main beam tracking error second signal (hereinafter referred to as “MTEN” signal).

  Of the four light receiving surfaces e, f, g, and h of the light detector 28 and the four light receiving surfaces i, j, k, and l of the light detector 45, the light receiving surface e signal, the light receiving surface i signal, and the light receiving surface The signal h and the signal on the light receiving surface 1 are added by the adder 109 via the amplifiers 107 and 110, respectively, and become the first sub beam tracking error first signal (hereinafter referred to as “STEP” signal). The signal of the light receiving surface g and the signal of the light receiving surface k, the signal of the light receiving surface f and the signal of the light receiving surface j are added by the adder 112 via the amplifiers 108 and 111, respectively, and are added to the second signal of the sub beam tracking error (hereinafter referred to as the signal). , Referred to as the “STEN” signal).

  The “MTE P” signal and the “MTE N” signal are subtracted by the subtractor 113 to become a first tracking error signal (hereinafter referred to as “MTE” signal). The “STEP” and “STEN” signals are subtracted by the subtractor 114 and amplified by the amplifier 115 to be a second tracking error signal (hereinafter referred to as “STE2” signal).

  A low frequency pass filter 120 and a CPU 119 are connected in parallel to the output terminal of the amplifier 115, and a switch 121 is connected in series with the low frequency pass filter 120. Also, one input / output end of the CPU 119 is connected to the switch 121, and whether or not the low-pass filter 120 is made to function by turning on / off the switch 121 according to the state of the output signal from the amplifier 115. decide. Here, when the low frequency pass filter 120 is made to function, the end a and the end b of the switch 121 are made conductive, and when not made to function, the end a and the end c of the switch 121 are made conductive.

  When the low frequency pass filter 120 is functioned, the “STE2” signal output from the amplifier 115 passes through the low frequency filter 120 so that the frequency component exceeding the rotational frequency component of the optical disk 5 is removed. As a result, the amplitude of the signal decreases. That is, the low frequency pass filter 120 generates a third tracking error signal (hereinafter referred to as “STE3” signal) by reducing the amplitude of the “STE2” signal while passing only the rotational frequency component of the optical disc 5. . Thus, the amplitude of the tracking error signal is reduced while maintaining the frequency component necessary for tracking control, so that the “STE3” signal that can be used in place of the “STE2” signal can be generated when the tracking error signal is generated.

  At this time, if the frequency that the low-pass frequency pass filter 120 passes is substantially the same as the maximum rotation frequency of the optical disc 5 that the optical disc apparatus can handle, the tracking control is performed when the “STE 3” signal is generated from the “STE 2” signal. Since only the necessary frequency components are maintained, high-precision tracking control according to the maximum number of rotations of the optical disk 5 that can be supported by the optical disk apparatus can be performed.

  The “MTE” signal becomes a tracking error signal (hereinafter referred to as “TE” signal) depending on whether the “STE2” signal or the “STE3” signal is subtracted by the subtractor 116. The amplitude value of the “TE” signal is adjusted. Thereafter, the “TE” signal drives the lens driving mechanism 15 via the filter 117 and the tracking driver 118.

When the gain of the amplifier 115 is “k”, the “TE” signal is
“TE” = “MTE” − “k” · “STE2” (Formula 6)
Or
“TE” = “MTE” − “k” · “STE3” (Formula 7)
The tracking control is performed by either (Expression 6) or (Expression 7).

  Here, “k” indicates that tracking control is being performed, and when the objective lens 4 moves in the radial direction from the midpoint position due to an eccentric component of the disk 5 or the like, an offset is generated in the push-pull signal and tracking control is performed. In order to prevent a state that cannot be maintained, this is a coefficient for equalizing the offset components of the main beam tracking error and the sub beam tracking error.

  4 and 5 are diagrams showing the main beam tracking error signal and the sub beam tracking error signal according to Embodiment 1 of the present invention. 4A and 5A show the main beam tracking error signal, FIGS. 4B and 5B show the sub beam tracking error signal, and the main beam tracking error signal and the sub beam shown in FIG. The relationship between the tracking error signals is opposite in phase, and the relationship between the main beam tracking error signal and the sub beam tracking error signal shown in FIG. 5 is in phase. 4 and 5, a is a predetermined amplitude value.

  When the phase relationship between the “MTE” signal and the “STE2” signal is opposite, the generated “TE” signal is as shown in FIG. In this case, since the “TE” signal represented by (Equation 6) has an amplitude value greater than or equal to the predetermined amplitude value a, tracking control using this “TE” signal is normally performed. When the “TE” signal can obtain an amplitude value greater than or equal to the predetermined amplitude value a, the CPU 119 performs tracking control without causing the low-frequency pass filter 120 to function.

  When the phase relationship between the “MTE” signal and the “STE2” signal is substantially the same, the generated “TE” signal is as shown in FIG. In this case, the “TE” signal represented by (Equation 6) becomes too small and does not have an amplitude value greater than or equal to the predetermined amplitude value a, and tracking control using this “TE” signal cannot operate normally. Therefore, when the “TE” signal cannot obtain an amplitude value greater than or equal to the predetermined amplitude value “a”, the CPU 119 performs the tracking control by functioning the low-frequency pass filter 120.

  When the CPU 119 switches the switch 121 to cause the low-frequency pass filter 120 to function, the “STE2” signal passes through the low-frequency pass filter 120 and the frequency component exceeding the rotational frequency component of the optical disc 5 is removed. Along with this, the amplitude of the signal decreases. At this time, the “STE2” signal changes to the “STE3” signal shown in FIG. 5D, and the “TE” signal becomes as shown in FIG. 5E. Tracking control using this “TE” signal is normally performed. Done. Therefore, even when the relationship between the “MTE” signal and the “STE2” signal is substantially the same phase, the CPU 119 can perform the tracking control by causing the low-frequency pass filter 120 to function.

  As described above, the CPU 119 determines whether or not to operate the low-pass filter 120 based on the amplitude difference between the output “MTE” signal and the “STE2” signal, and outputs the “TE” signal according to the situation. The signals used for generation, that is, the “STE2” signal and the “STE3” signal are selectively used.

  That is, the CPU 119 determines whether or not the low frequency pass filter 120 is functioning when the “TE” signal generated in (Equation 6) exceeds the predetermined amplitude value a. If the “TE” signal generated in (Equation 6) does not exceed the predetermined amplitude value a, the low-pass filter 120 is activated, and the “TE” signal is generated in (Equation 7) for tracking control. Use.

  When the generated “TE” signal exceeds the predetermined amplitude value “a”, the “MTE” signal and the “STE2” signal are almost in the same phase. It is also possible to measure the phase. In this way, the CPU 119 only measures and compares the phase of the “MTE” signal and the phase of the “STE2” signal without actually calculating the “MTE” signal from the “MTE” signal and the “STE2” signal. Since it is determined whether or not the “TE” signal exceeds a predetermined amplitude value, it is easy to determine whether to use the “STE2” signal or the “STE3” signal when generating the “TE” signal. Moreover, it can be determined in a short time.

  Further, when the difference between the phase of the “MTE” signal and the phase of the “STE2” signal is 20 degrees or less, the CPU 119 determines that the phase of the “MTE” signal and the phase of the “STE2” signal are substantially the same phase. Thus, the CPU 119 determines whether the phase of the “MTE” signal and the phase of the “STE2” signal are substantially the same without accurately measuring the phase of the “MTE” signal and the phase of the “STE2” signal. Therefore, it can be determined in a shorter time with a simpler configuration.

  FIG. 6 is a flowchart showing tracking control in the first embodiment of the present invention.

  When the optical disk 5 is loaded in the optical disk apparatus, the CPU 119 rotates the spindle motor 206 via the spindle driver 216a and causes the light source 1 to emit light via the laser driver 216b (S1). The light emitted from the light source 1 reaches the diffraction grating 39 via the collimator lens 2, and is split into three light beams of the main beam, the first sub beam, and the second sub beam when passing through the diffraction grating 39. (S2).

  The three separated light beams reach the optical disk 5 via the beam splitter 40 and the objective lens 4, and a part of the reached light is reflected. The reflected light passes through the objective lens 4, the beam splitter 40, and the focusing lens 9, and the main beam is one of the photodetector 25, the first sub beam is the photodetector 28, and the second sub beam is the photodetector 45. Is received. Thereafter, the signal processing circuit 100 generates an “MTE” signal (first tracking error signal) based on the output signal of the photodetector 25 (S3), and the “STE2” signal based on the output signals of the photodetectors 28 and 45. (Second tracking error signal) is generated (S4).

  Here, the CPU 119 subtracts the “STE2” signal from the generated “MTE” signal, and compares the subtraction result with the predetermined amplitude value a (S5). At this time, if the subtraction result exceeds the predetermined value a, the “TE” signal is calculated by (Equation 6) (S6), and tracking control is performed using the “TE” signal (S9).

  On the other hand, when the subtraction result does not exceed the predetermined amplitude value a, the “STE3” signal is extracted from the “STE2” signal using the low-pass frequency pass filter 120 (S7). Then, the “TE” signal is calculated by (Equation 7) (S8), and tracking control is performed using the “TE” signal (S9).

  As described above, the light emitted from the light source is split into a main beam and a sub beam having a phase different from that of the main beam, and an “MTE” signal is obtained based on the main beam that reaches the optical disc and is reflected from the optical disc. Is generated, the “STE2” signal is generated based on the sub-beam that reaches the optical disc and is reflected from the optical disc, passes the “STE2” signal below a predetermined frequency, extracts the “STE3” signal, and outputs the “MTE” signal. When the “TE” signal does not exceed a predetermined amplitude value when the “TE2” signal is generated by subtracting the “STE2” signal from the “STE2” signal, the “STE3” signal is used instead of the “STE2” signal. By generating the signal, the signal used for generating the “TE” signal is selectively used depending on whether the “TE” signal exceeds the predetermined amplitude value or not. Therefore, the amplitude value of the “TE” signal is always constant. It can be kept circumference, the "TE" signal without influence of phase values for the main beam of the sub-beams can be generated. As a result, the “TE” signal is generated without being affected by the phase value of the sub beam with respect to the main beam, so the phase of the sub beam with respect to the main beam changes depending on the temperature change of the use environment or the recording or reproduction position on the optical disk. Even in this case, it is possible to realize an optical disc apparatus that always maintains highly accurate tracking control and its tracking control.

(Embodiment 2)
In the second embodiment of the present invention, a case where the cutoff frequency of the low-frequency pass filter 120 is switched according to the number of rotations of the rotation driving means for rotating the optical disk will be described with reference to the drawings.

  The overall configuration of the optical disc apparatus according to the second embodiment is the same as that of the first embodiment shown in FIGS. Further, the main beam tracking error signal and the sub beam tracking error signal in the second embodiment are the same as those in the first embodiment shown in FIGS. 4 and 5 except for noise components generated due to partial eccentricity. In the second embodiment, the light source is the light source 1, the rotation driving means is the spindle motor 206, the spectroscopic means is the diffraction grating 39, the control means is the CPU 119, the first tracking error signal generating means is the subtractor 113, and the second tracking error signal. The generation means corresponds to the subtractor 114, and the filter corresponds to the low-frequency pass filter 120, which is the same as in the first embodiment.

  FIG. 7 is a diagram showing a low-pass frequency pass filter according to Embodiment 2 of the present invention. In FIG. 7, 121d, 121e, 121f, and 121g are end portions, R1, R2, and R3 are resistors, and C is a capacitor.

  The switch 121 has a plurality of end portions 121d, 121e, 121f, and 121g, and the end portion 121d of the switch 121 is electrically connected to any one of the end portion 121e, the end portion 121f, and the end portion 121g, thereby providing a low-frequency pass filter. 121 circuit constants can be switched. For example, when the end portion 121d and the end portion 121e are made conductive, the low frequency pass filter 120 is formed by the resistor R1 and the capacitor C.

  Hereinafter, a method of generating a signal corresponding to the “STE3” signal in the first embodiment from the “STE2” signal using the low-frequency pass filter 120 shown in FIG. 7 will be described.

  When the phase relationship between the “MTE” signal and the “STE2” signal is opposite, the generated “TE” signal is as shown in FIG. In this case, since the “TE” signal represented by (Equation 6) has an amplitude value greater than or equal to the predetermined amplitude value a, tracking control using this “TE” signal is normally performed. When the “TE” signal can obtain an amplitude value greater than or equal to the predetermined amplitude value a, the CPU 119 performs tracking control without causing the low-frequency pass filter 120 to function.

  When the phase relationship between the “MTE” signal and the “STE2” signal is substantially the same, the generated “TE” signal is as shown in FIG. In this case, the “TE” signal represented by (Equation 6) becomes too small and does not have an amplitude value greater than or equal to the predetermined amplitude value a, and tracking control using this “TE” signal cannot operate normally. Therefore, when the “TE” signal cannot obtain an amplitude value greater than or equal to the predetermined amplitude value “a”, the CPU 119 performs the tracking control by functioning the low-frequency pass filter 120.

  When the CPU 119 switches the switch 121 to make the low-pass filter 120 function, the “STE2” signal passes through the low-pass filter 120, and the frequency component exceeding the rotational frequency component of the optical disc is removed. This reduces the signal amplitude. In addition, although the switch 121 in this Embodiment 2 can switch 3 types, it is not limited to this. When the end 120d and the end 120e are made conductive, the low-pass filter 120 is formed by the resistor R1 and the capacitor C. When the end 120d and the end 120f are made conductive, the resistor R2 and the capacitor C are used. When the low-pass filter 120 is formed and the end 120d and the end 120g are made conductive, the low-pass filter 120 is formed by the resistor R3 and the capacitor C.

  FIG. 8 is a diagram showing area division of the optical disc in the second embodiment of the present invention. In FIG. 8, 5 is an optical disk.

  The CPU 119 divides the optical disk 5 into a plurality of areas according to the radius amount, and performs tracking control. In the second embodiment, tracking control is performed with a plurality of regions as three regions 131, 132, and 133, but is not limited to this. The three areas in the second embodiment correspond to the switching classification of the Zone Constant Linear Velocity method (hereinafter referred to as the ZCLV method). Since the region 131 is located on the inner peripheral side of the optical disc 5, the rotational speed of the spindle motor 206 is increased, and since the region 133 is located on the outer peripheral side of the optical disc 5, the rotational number of the spindle motor 206 is decreased.

  Some optical discs 5 have a partial eccentricity in which a track located on a recording surface is partially deviated from an ideal trajectory. This partial eccentricity is affected as a noise component when the tracking error signal is generated, and the manner of the influence varies depending on the rotation speed of the spindle motor 206.

  FIG. 9 is a diagram showing a tracking error signal in the case of single switching in which the switch is only on / off. FIG. 9 shows a tracking error signal when an optical disk having partial eccentricity is used. FIG. 9A shows a tracking error signal obtained from the region 131 shown in FIG. 8, and FIG. FIG. 9C shows a tracking error signal obtained from the region 132 shown in FIG. 8, and FIG. 9C shows a tracking error signal obtained from the region 133 shown in FIG. In FIG. 9, 134 is noise. FIG. 10 is a diagram showing a tracking error signal when the switch according to Embodiment 2 of the present invention is used. FIG. 10 shows a tracking error signal when an optical disk having partial eccentricity is used. FIG. 10A shows a tracking error signal obtained from the area 131 shown in FIG. 8, and FIG. FIG. 10C shows a tracking error signal obtained from the region 132 shown in FIG. 8, and FIG. 10C shows a tracking error signal obtained from the region 133 shown in FIG.

  When the optical disk 5 has partial eccentricity and the optical disk is rotated at a plurality of speeds, the frequency of the “TE” signal changes according to the rotation speed of the spindle motor 206. At this time, the frequency of the noise caused by the partial eccentricity also changes, and the noise may or may not pass depending on the circuit constant setting method of the low-frequency pass filter 120. The noise caused by the partial eccentricity is not preferable because the main beam shifts from the center position of the track when performing tracking control using the “TE” signal, which causes troubles in recording and reproduction.

  Usually, the circuit constant of the low-frequency pass filter 120 is set so as to be compatible when the region 131 of the optical disk 5 is used, that is, when the rotational speed of the spindle motor 206 is the highest. For example, in the case of a quadruple speed DVD, the cut-off frequency of the low-frequency pass filter 120 is set to about 190 Hz corresponding to a cycle that is twice the rotational speed. When this cut-off frequency is used in the region 132 or the region 133 of the optical disc 5, the frequency necessary for generating the “TE” signal can be ensured, but noise due to partial eccentricity is included. This is because the frequency of noise caused by partial eccentricity changes depending on the rotation speed of the spindle motor 206.

  Therefore, when used in the area 132 or the area 133 of the optical disc 5, only a frequency necessary for generating the “TE” signal is secured, and a different cutoff frequency is set so that noise due to partial eccentricity cannot pass. It is preferable. For example, in the case of a quadruple speed DVD, when using the region 132, the cut-off frequency is set to about 130 Hz corresponding to a cycle that is twice the rotation speed, and when using the region 133, the cut-off frequency is rotated. It is set to about 70 Hz, which corresponds to a period twice the number.

  Therefore, in the second embodiment, the cut-off frequency of the low-frequency pass filter 120 is switched by switching the end portion to which the end portion 121d of the switch 121 is connected to any one of the end portion 121e, the end portion 121f, and the end portion 121g. Can be set multiple times. With such a configuration, the characteristics of the low-frequency pass filter 120 can be changed in accordance with the region used by the optical disk 5, that is, the rotational speed of the spindle motor 206. As a result, even when the optical disc 5 has partial eccentricity, the “TE” signal shown in FIG. 10 can be generated without generating the noise 134 shown in FIG. 9, and the “TE3” signal is generated from the “TE2” signal. In this case, only the frequency components necessary for tracking control are maintained, so that highly accurate tracking control can be performed according to the rotational speed of the optical disk 5.

  FIG. 11 is a flowchart showing tracking control in the second embodiment of the present invention.

  When the optical disk 5 is loaded in the optical disk apparatus, the CPU 119 rotates the spindle motor 206 via the spindle driver 216a and causes the light source 1 to emit light via the laser driver 216b (S11). The light emitted from the light source 1 reaches the diffraction grating 39 via the collimator lens 2, and is split into three light beams of the main beam, the first sub beam, and the second sub beam when passing through the diffraction grating 39. (S12).

  The three separated light beams reach the optical disk 5 via the beam splitter 40 and the objective lens 4, and a part of the reached light is reflected. The reflected light passes through the objective lens 4, the beam splitter 40, and the focusing lens 9, and the main beam is one of the photodetector 25, the first sub beam is the photodetector 28, and the second sub beam is the photodetector 45. Is received. Thereafter, the signal processing circuit 100 generates an “MTE” signal (first tracking error signal) based on the output signal of the photodetector 25 (S13), and the “STE2” signal based on the output signals of the photodetectors 28 and 45. (Second tracking error signal) is generated (S14).

  Here, the CPU 119 subtracts the “STE2” signal from the generated “MTE” signal, and compares the subtraction result with the predetermined amplitude value a (S15). At this time, if the subtraction result exceeds the predetermined value a, the “TE” signal is calculated by (Equation 6) (S16), and tracking control is performed using the “TE” signal (S25).

If the subtraction result does not exceed the predetermined amplitude value a, the CPU 119 first checks whether the objective lens 4 follows the track in the area 131 of the optical disk 5 (S17). At this time, when the objective lens 4 follows the track of the area 131 of the optical disk 5, the CPU 119 changes the circuit constant of the low-frequency pass filter 120 by switching to the state of the switch 121 corresponding to the area 131 of the optical disk 5. Then, a fourth tracking error signal (hereinafter referred to as “STE4” signal) is extracted from the “STE2” signal (S18). And the “TE” signal
“TE” = “MTE” − “k” · “STE4” (Formula 8)
(S19), and tracking control is performed using the “TE” signal (S25).

If the subtraction result does not exceed the predetermined amplitude value a and the objective lens 4 does not follow the track of the area 131 of the optical disc 5, the CPU 119 then follows the track of the area 132 of the optical disc 5. (S20). At this time, if the objective lens 4 follows the track of the area 132 of the optical disc 5, the CPU 119 changes the circuit constant of the low-frequency pass filter 120 by switching to the state of the switch 121 corresponding to the area 132 of the optical disc 5. Then, a fifth tracking error signal (hereinafter referred to as “STE5” signal) is extracted from the “STE2” signal (S21). And the “TE” signal
“TE” = “MTE” − “k” · “STE5” (Formula 9)
(S22) and tracking control is performed using the "TE" signal (S25).

If the subtraction result does not exceed the predetermined amplitude value a and the objective lens 4 does not follow any of the tracks in the area 131 and the area 132 of the optical disk 5, the CPU 119 causes the objective lens 4 to track the area 133 of the optical disk 5. Is switched to the state of the switch 121 corresponding to the region 132 of the optical disk 5 to change the circuit constant of the low-frequency pass filter 120, and the sixth tracking error signal (hereinafter referred to as “STE2” signal). The “STE6” signal is extracted (S23). And the “TE” signal
“TE” = “MTE” − “k” · “STE6” (Equation 10)
(S24), and tracking control is performed using the "TE" signal (S25).

  The “STE4” signal, the “STE5” signal, or the “STE7” signal in the second embodiment corresponds to the third tracking error signal in the first embodiment.

  Here, the rotation speed of the spindle motor 206 differs depending on which of the region 131, the region 132, and the region 133 includes the region where the track that the objective lens 4 follows is located. Therefore, by switching the cut-off frequency of the low-frequency pass filter 120 in accordance with the number of rotations of the spindle motor 206, only the frequency component necessary for tracking control when generating the third tracking error signal from the second tracking error signal. Therefore, tracking control with high accuracy can be performed according to the number of rotations of the optical disk 5.

  As described above, the light emitted from the light source is split into a main beam and a sub beam having a phase different from that of the main beam, and an “MTE” signal is obtained based on the main beam that reaches the optical disc and is reflected from the optical disc. Is generated on the basis of the sub-beam that reaches the optical disc and is reflected from the optical disc, and passes below the predetermined frequency of the “STE2” signal, which corresponds to the third tracking error signal in the first embodiment. When the “STE4” signal, the “STE5” signal, or the “STE7” signal is extracted and the “STE2” signal is subtracted from the “MTE” signal to generate the “TE” signal, When the “TE” signal does not exceed the predetermined amplitude value, either the “STE4” signal, the “STE5” signal, or the “STE7” signal is substituted for the “STE2” signal. By generating the “TE” signal using the “TE” signal, the signal used when generating the “TE” signal is selectively used depending on whether the “TE” signal exceeds the predetermined amplitude value or not. The amplitude value of the signal can always be kept within a certain range, and the “TE” signal can be generated without being affected by the phase value of the sub beam with respect to the main beam. As a result, the “TE” signal is generated without being affected by the phase value of the sub beam with respect to the main beam, so the phase of the sub beam with respect to the main beam changes depending on the temperature change of the use environment or the recording or reproduction position on the optical disk. Even in this case, it is possible to realize an optical disc apparatus that always maintains highly accurate tracking control and its tracking control.

  The present invention is capable of always maintaining highly accurate tracking control even when the temperature of the usage environment changes, and an optical disc apparatus that records and / or reproduces information on an optical disc, a tracking control method thereof, and the like Can be adapted to.

1 is a block diagram of an optical disc apparatus according to Embodiment 1 of the present invention. The figure which shows the optical pick-up apparatus in Embodiment 1 of this invention The figure which shows the structure of the focus drive device in Embodiment 1 of this invention. The figure which shows the main beam tracking error signal and sub beam tracking error signal in Embodiment 1 of this invention The figure which shows the main beam tracking error signal and sub beam tracking error signal in Embodiment 1 of this invention The flowchart which shows the tracking control in Embodiment 1 of this invention. The figure which shows the low-pass frequency pass filter in Embodiment 2 of this invention The figure which shows the area division of the optical disk in Embodiment 2 of this invention The figure which shows the tracking error signal when the switch is only on / off switching The figure which shows the tracking error signal at the time of utilizing the switch in Embodiment 2 of this invention Flowchart showing tracking control in Embodiment 2 of the present invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Light source 2 Collimator lens 4 Objective lens 5 Optical disk 9 Focusing lens 11 Amplifier 15 Lens drive mechanism 15a Coil 25 for tracking adjustment 25, 28 Photo detector 39 Diffraction grating 40 Beam splitter 41, 42, 43 Condensing spot 45 Photo detector 48, 49, 50 Light spot 100 Signal processing circuit 101, 102, 103, 104 Amplifier 105, 106 Adder 107, 108 Amplifier 109 Adder 110 Amplifier 112, 113, 114 Subtractor 115 Amplifier 116 Subtractor 117 Filter 118 Tracking driver 119 CPU
120 Low-pass filter 121 Switch 121a, 121b, 121c, 121d, 121e, 121f, 121g End 123 Amplifier circuit 131, 132, 133 Region 134 Noise 203 Lens holder 206 Spindle motor 207 Feed motor 216a Spindle driver 216b Laser driver 300 Optical head part 400 Pickup module

Claims (10)

A light source;
A spectroscopic means for splitting light emitted from the light source into a main beam and a sub beam having a phase different from that of the main beam;
First tracking error signal generating means for generating a first tracking error signal based on the main beam reflected from the optical disk after reaching the optical disk;
Second tracking error signal generating means for generating a second tracking error signal based on the sub beam reflected from the optical disk after reaching the optical disk;
A filter that passes a predetermined frequency or less of the second tracking error signal and extracts a third tracking error signal;
Control means for generating a tracking error signal by subtracting the second tracking error signal from the first tracking error signal;
The optical disc apparatus, wherein the control means generates a tracking error signal using the third tracking error signal instead of the second tracking error signal when the tracking error signal does not exceed a predetermined amplitude value. The control means determines that the tracking error signal does not exceed a predetermined amplitude value when the phase of the first tracking error signal and the phase of the second tracking error signal are substantially the same. The optical disk device described. When the difference between the phase of the first tracking error signal and the phase of the second tracking error signal is 20 degrees or less, the control means determines that the phase of the first tracking error signal and the phase of the second tracking error signal are 3. The optical disc apparatus according to claim 2, wherein it is determined that the phases are substantially the same. Rotation drive means for rotating the optical disc,
2. The optical disc apparatus according to claim 1, wherein the filter generates the third tracking error signal by reducing the amplitude of the second tracking error signal while allowing only the rotational frequency component of the optical disc to pass therethrough. 5. The optical disk apparatus according to claim 4, wherein the predetermined frequency of the filter is switched according to the number of rotations of the rotation driving means. The light emitted from the light source is split into a main beam and a sub beam having a phase different from that of the main beam, and a first tracking error signal is generated based on the main beam reflected from the optical disc after reaching the optical disc. Generating a second tracking error signal based on the sub-beam reflected from the optical disk after reaching the optical disk, passing a frequency equal to or lower than a predetermined frequency of the second tracking error signal, and extracting a third tracking error signal; When generating the tracking error signal by subtracting the second tracking error signal from the first tracking error signal,
When the tracking error signal does not exceed a predetermined amplitude value, a tracking error signal is generated using a third tracking error signal instead of the second tracking error signal. 7. The tracking of an optical disc apparatus according to claim 6, wherein when the phase of the first tracking error signal and the phase of the second tracking error signal are substantially the same, it is determined that the tracking error signal exceeds a predetermined amplitude value. Control method. When generating the tracking error signal by subtracting the second tracking error signal from the first tracking error signal,
When the difference between the phase of the first tracking error signal and the phase of the second tracking error signal is 20 degrees or less, the phase of the first tracking error signal and the phase of the second tracking error signal are substantially in phase. 8. The tracking control method for an optical disc apparatus according to claim 7, wherein the tracking control method is determined as follows. When the third tracking error signal is extracted by passing the second tracking error signal below a predetermined frequency,
7. The tracking control method for an optical disc apparatus according to claim 6, wherein the third tracking error signal is generated by reducing the amplitude of the second tracking error signal while allowing only the rotational frequency component of the optical disc to pass. 7. The tracking control method for an optical disc apparatus according to claim 6, wherein the predetermined frequency is substantially the same as a maximum rotation frequency of the optical disc.

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