JP2006228356A - Optical disk device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an optical disk device in which stable reproduction can be achieved by detecting stain such as dust and finger prints or the like on a disk and inputting respectively corresponding control signals to a PLL circuit. <P>SOLUTION: A total signal, which is a total reflection amount from an optical disk, is converted into control signals having equal to or greater than three values in accordance with the strength of the total signal. Then, when reduction in the RF signal level is large by the existence of dust or the like, conventional operation hold is conducted for the PLL circuit. When reduction in the RF signal level is small for the case of stain such as finger prints or the like, the gain of the PLL circuit is switched to prevent occurrence of a hypersensitive response of the PLL circuit within the range. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to an optical disc apparatus intended to stably reproduce information recorded on an optical disc.

  In the conventional optical disk apparatus, when dust is present on the surface of the optical disk, a decrease in the total signal in the area where the dust is present is detected and the operation of the PLL circuit is held to avoid an abnormal response of the PLL circuit in the area. However, stable reproduction of information recorded on the optical disk is performed.

  FIG. 11 shows a configuration of a conventional optical disc apparatus having a function of detecting the presence of dust on the optical disc surface and avoiding an abnormal response of the PLL circuit.

  As shown in FIG. 11, the optical disc apparatus first rotates the optical disc (1103) by the spindle motor (1102) under the control of the motor control circuit (1101), and then the optical pickup RF amplifier section (1104). ) Is controlled so as to focus on the information recording surface on the optical disk by the servo control circuit (1105), and at the same time, while controlling to track a predetermined track position on the optical disk. Then, the RF signal that is the recording information signal and the total signal that is the total reflected light amount on the optical disc are extracted from the light that is irradiated onto the optical disc surface and reflected from the optical disc, and then the RF signal is binarized (1106) In the PLL circuit (1107), a reference clock is extracted from the binarized signal, and a demodulating circuit ( 108) in on the basis of the reference clock is performed demodulation. In the PLL circuit, the optical disc apparatus first compares the binarized signal input from the binarizing circuit with the output signal of the voltage controlled oscillator (hereinafter referred to as VCO) (1112) by the phase comparator (1109). Then, a signal corresponding to the phase difference is output, then a current corresponding to the phase difference signal is output by the charge pump (1110), and subsequently, a low pass filter (hereinafter referred to as LPF) (1111). Only the low-frequency component is passed through and output to the VCO. Finally, the VCO oscillates the PLL clock at a frequency proportional to the input voltage. This PLL clock becomes a detection clock when demodulating the binarized data.

  On the other hand, the optical disk apparatus slices the total signal at a predetermined slice level by the comparator (1113), generates the data as a slice signal, outputs it to the servo controller (1114), and processes it into a control signal by the servo controller. Then, it is supplied to the charge pump of the PLL circuit.

Here, when almost no RF signal is generated due to dust existing on the optical disc, the PLL circuit is held in operation by a control signal based on the total signal that decreases in the region. The operation hold of the PLL circuit opens the output current of the charge pump, preventing the VCO's sensitive response in the dusty area. With such a function, the conventional optical disc apparatus avoids an abnormal response of the PLL circuit due to dust on the surface of the optical disc and enables stable reproduction.
JP-A-10-162364

  However, when the decrease in the RF signal is small compared to dust, such as dirt due to fingerprints, the operation of the PLL circuit is not held because the decrease in the total signal in that region is not detected. As a result, there is a problem that the reproduction performance of the binarized signal is deteriorated due to the low RF signal in the dirt region due to fingerprints and the like, and the reproduction performance cannot be stabilized because the PLL circuit responds abnormally. It was.

  In view of such circumstances, the present invention makes the presence of signals such as dust or scratches on the disk surface (hereinafter referred to as dust) by making the total signal a control signal of three or more values according to the intensity. If the RF signal level is not generated in the area where the signal is generated or if the decrease is large, the operation of the PLL circuit is held as before, and if the decrease in the RF signal level is small, such as dirt due to fingerprints, the PLL circuit Provided is an optical disc apparatus which has a function of preventing a sensitive response of a PLL circuit in the region by switching the gain, and can perform stable reproduction corresponding to various dusts on the disc and dirt due to fingerprints.

  By making the total signal a control signal having three or more values according to the intensity as in the present invention, it is possible to perform various controls on the PLL circuit. For example, even when the decrease in the RF signal level is small, such as dirt due to fingerprints, a control signal corresponding to the level is input to the PLL circuit, and the gain of the PLL circuit is reduced, etc. By preventing a sensitive response, it is possible to provide an optical disc apparatus capable of performing stable reproduction corresponding to various dusts on the disc and dirt due to fingerprints.

  The best mode for carrying out each invention will be described below. The present invention is not limited to these embodiments, and can be implemented in various ways without departing from the scope of the invention. The first embodiment will mainly describe claim 1 and the like. In the second embodiment, claim 2 will be mainly described. In the third embodiment, claim 3 will be mainly described. In the fourth embodiment, claim 4 will be mainly described.

  << Embodiment 1 >>

  <Embodiment 1: Overview> An optical disc apparatus according to the present embodiment is based on a conventional optical disc apparatus and is converted into a ternary signal in accordance with the total signal intensity from the optical pickup RF amplifier unit as total signal intensity information. The optical disk apparatus is characterized in that a PLL circuit is operated by a control signal based on information. In the conventional optical disc apparatus, the operation of the PLL circuit is controlled by the binarized total signal intensity information. By making the total signal strength information a ternary signal according to the present invention, the PLL circuit can be controlled more variously.

  <Embodiment 1: Configuration> FIG. 1 shows an example of a functional block diagram of an optical disc apparatus according to the present embodiment. The optical disk apparatus according to the first embodiment includes an “optical pickup RF amplifier unit” (0101), a “total signal intensity information acquisition unit” (0102), and an “RF demodulation PLL circuit system unit” (0103).

  The “optical pickup RF amplifier unit” (0101) is a unit that irradiates a light beam onto the optical disc (0104), receives the light reflected by the optical disc, generates an RF signal and a total signal, and outputs them. The optical pickup RF amplifier unit has an optical pickup and an RF amplifier. The “optical pickup” has a function of generating a reproduction RF signal and a total signal after irradiating a light beam onto an optical disk and receiving reflected light. The “reproduced RF signal” is a signal obtained by detecting reflected light from the optical disc with a light receiving element and converting it into a current, and corresponds to a reproduced signal as information recorded on the optical disc. “Total signal” refers to a signal obtained by converting the total amount of reflected light from the optical disk into a current. The “total signal strength” is the strength of the total signal, and corresponds to the voltage value of the total signal, digital information indicating the size of the total signal, or the like. Accordingly, the total signal intensity is reduced in an area where dust or the like, or dirt due to a fingerprint or the like exists on the disc. The “RF amplifier” has a function of generating an RF signal by performing arithmetic processing on the reproduction RF signal detected by the optical pickup. The “RF signal” is a signal obtained by voltage-converting the reproduction RF signal generated by the optical pickup.

  The “total signal strength information acquisition unit” (0102) is a unit that acquires the total signal from the optical pickup RF amplifier unit as total signal strength information that is a ternary signal. The total signal strength information acquisition unit is configured by a circuit that, after dividing into three according to the value of the total signal, acquires total signal strength information converted into a ternary signal for each divided region and outputs a control signal. ing. The “ternary signal” is a signal obtained by dividing the total signal intensity into three parts according to the value. For example, when the total signal intensity is divided into “a certain range”, “above the certain range”, and “below the certain range” according to the value, each is divided into “0”, “1”, “−1”. The signal converted into ternary values such as. However, the method for dividing the total signal intensity is not a problem. Information in which the total signal intensity is converted into a ternary signal is referred to as “total signal intensity information”. The “control signal” is a signal output to the RF demodulation PLL circuit system unit based on the total signal strength information. As the control signal, two or more of the three signals based on the total signal intensity information which is the ternary signal may be output. For example, the total signal strength information acquisition unit is connected to the RF demodulation PLL circuit system unit as in the case where the total signal strength indicated by A in FIG. Therefore, when it is not necessary to perform control, the control signal based on the total signal strength information corresponding to the total signal strength may not be output.

  The “RF demodulation PLL circuit system unit” (0103) is a unit that operates based on the RF signal from the optical pickup RF amplifier unit and the total signal strength information acquired by the total signal strength information acquisition unit. . The RF demodulation PLL circuit system unit has a function of outputting a demodulation signal to the demodulation circuit after extracting a reproduction reference clock from the RF signal. The RF demodulation PLL circuit system section is composed of a binarization circuit (0105) and a PLL circuit (0106). The “binarization circuit” (0105) is a circuit that extracts rising and falling edges of the waveform from the RF signal read from the optical disc, and generates a binarization signal depending on the presence or absence of the edge. The “PLL circuit” (0106) detects the phase difference between the binarized signal acquired from the binarized circuit and the output signal from the VCO, and applies feedback control so that the phase is the same phase. This circuit oscillates a signal. It is possible to oscillate a signal that is accurately synchronized by the PLL circuit. The configuration and internal operation of the PLL circuit in this embodiment will be described below. The PLL circuit includes a phase comparator (0107), a charge pump (0108), an LPF (0109), and a VCO (0110). The “phase comparator” (0107) compares the phase difference between the binarized signal acquired from the binarization circuit and the output signal from the VCO, and uses the phase difference component of the two signals as a phase difference signal. Has a function to output. The “charge pump” (0108) is a voltage converter to which a capacitor is applied, and has a function of acquiring a phase difference signal from the phase comparator and outputting a current corresponding to the phase difference signal. The charge pump has a function of controlling the operation of the PLL circuit by acquiring two or more control signals output from the total signal strength information acquisition unit and switching the output current based on the control signals. . The charge pump of this embodiment is characterized in that the output current can be switched in two stages, unlike the PLL circuit of the conventional optical disc apparatus. “LPF” (0109) is an electrical filter that attenuates the high frequency component of the current output from the charge pump and passes only the low frequency component. “VCO” (0110) has a function of oscillating a PLL clock at a frequency proportional to the voltage output from the LPF. The output signal from the phase comparator controls the VCO via the charge pump and LPF, thereby synchronizing with the phase of the binarized signal acquired from the binarization circuit. The PLL clock thus transmitted is used as a reference clock when demodulating the binary signal.

  <Embodiment 1: Process Flow> FIG. 2 is a flowchart showing an example of a process flow in the present embodiment. First, a light beam is irradiated onto the optical disc from the optical pickup RF amplifier unit (light beam irradiation step S0201). Next, the light reflected by the optical disk is received by the optical pickup RF amplifier unit (reflected light receiving step S0202). Subsequently, the light received in the reflected light receiving step is output as an RF signal to the RF demodulation PLL circuit system unit (RF signal output step S0203). Further, the light received in the reflected light receiving step is output to the total signal intensity information acquisition unit as a total signal (total signal output step S0204). Further, the total signal output in the total signal output step is acquired by a total signal strength information acquisition unit (total signal acquisition step S0205). Next, the acquired total signal is converted into a ternary signal according to the intensity, and total signal intensity information is acquired. (Total signal strength information acquisition step S0206). Subsequently, a control signal is acquired based on the total signal strength information acquired in the total signal strength information acquisition step (control signal acquisition step S0207). Further, the control signal acquired in the control signal generation step is output to the PLL circuit of the RF demodulation PLL circuit system unit (control signal output step S0208). Then, the RF signal output in the RF signal output step is acquired by the binarization circuit of the RF demodulation PLL circuit system unit (RF signal acquisition step S0209). Next, the RF signal acquired in the RF signal acquisition step is converted into a binarized signal by the binarization circuit (binarized signal conversion step S0210). Subsequently, the binarized signal generated in the binarized signal conversion step and the output signal from the VCO of the PLL circuit are acquired in the phase difference comparator of the PLL circuit, and the phase difference between the two signals is acquired. Based on the above, a phase difference signal is generated (phase difference signal generation step S0211). Then, the control signal output in the control signal output step is acquired by a PLL circuit (control signal acquisition step S0212). Then, the output current from the charge pump is switched based on the control signal acquired in the control signal acquisition step (output current switching step S0213). Next, the phase difference signal generated in the phase difference signal generation step is acquired, and a current corresponding to the phase difference signal and switching of the output current in the output current switching step is output from the charge pump ( Charge pump current output step S0214). Subsequently, the high-frequency component of the current output in the charge pump current output step is removed by a low-pass filter (high-frequency component removal step S0215). Finally, the VCO oscillates the PLL clock to the demodulation circuit at a frequency proportional to the voltage input from the high frequency component removal step (PLL clock oscillation step S0216).

<Embodiment 1: Brief description of effect>
In the conventional optical disk apparatus, the operation of the PLL circuit is controlled mainly by the binarized total signal intensity information. By controlling the total signal strength information to a ternary signal according to the present invention, control over the PLL circuit becomes more diverse.

  << Embodiment 2 >>

  <Embodiment 2: Overview> Based on the results of the optical disc apparatus of Embodiment 2, the total signal strength information acquisition unit slices the total signal at two slice levels based on the strength based on Embodiment 1. Thus, an optical disk apparatus is characterized in that a ternary signal is acquired.

  <Embodiment 2: Configuration> FIG. 3 shows an example of a functional block diagram of an optical disk apparatus according to this embodiment. As shown in this figure, the optical disc apparatus according to the present embodiment is based on the first embodiment, and includes an “optical pickup RF amplifier unit” (0301), a “total signal intensity information acquisition unit” (0302), and an “RF demodulation”. PLL circuit system section ”(0303). In the present embodiment, the total signal intensity information acquisition unit further includes a “comparator unit” (0304) and a “ternary unit” (0305) as its features. Note that the description of the functions of the “optical pickup RF amplifier unit” and the “RF demodulation PLL circuit system unit” in the present embodiment is the same as that in the first embodiment, and is omitted. Hereinafter, a characteristic point of the present embodiment in the “total signal strength information acquisition unit” will be described.

  "Comparator means" (0304) is means for slicing the total signal from the optical pick RF amplifier unit at two slice levels according to its strength and generating a comparator output signal for each slice level.

  The comparator means includes, for example, two comparators (comparator α 0306 and comparator β 0307), and each comparator slices the total signal at different slice levels based on its strength. Each comparator compares the slice level set to itself with the total signal strength sliced at the slice level, and the comparison result of whether the sliced total signal strength is higher or lower than the slice level. To generate a comparator output signal. The “comparator output signal” is a signal generated based on the comparison result. For example, if the sliced total signal strength is higher than the slice level at which the total signal strength is sliced, a comparator output signal such as “OVER” is generated from the comparison result of each comparator. Also good.

  The two slice levels may be determined assuming, for example, a total signal level that decreases in response to dust on the disk and a total signal level that decreases in response to contamination due to fingerprints. As a specific example, as shown in FIG. 4, the comparator α slices the total signal at a low level corresponding to dust (0401) on the disk (slice level 1: below, referred to as SL1) (0403). . Further, the comparator β slices the total signal at a low level corresponding to dirt (0402) due to a fingerprint or the like (slice level 2: hereinafter referred to as SL2) (0404). Here, SL2 is higher than SL1, but is lower than the normal total signal intensity level (0405) when there is no dust or dirt.

  “Ternization means” (0305) is means for acquiring total signal intensity information, which is the ternary signal, based on comparator output signals for two slice levels generated by the comparator means. For example, as shown in FIG. 5, the combination of the comparator output signals generated at each of SL1 and SL2 in the comparator means is represented by “SL1: SL2 as represented by each time point A, B, C in FIG. Are “OVER: OVER”, “OVER: UNDER”, and “UNDER: UNDER”. Accordingly, a ternary signal such as “0”, “1”, “2”, or the like may be generated for each of the combinations. Information obtained by converting the comparator output signal into a ternary signal is referred to as “total signal strength information”. A signal output to the RF demodulation PLL circuit system unit based on the total signal strength information is referred to as a “control signal”.

  The total signal strength information acquisition unit in the present embodiment can extend the transmission of the control signal for a predetermined period when outputting the control signal to the PLL circuit of the PLL circuit system unit for RF demodulation. An example will be described with reference to FIG. First, if the level of the total signal intensity is a decrease that does not affect reproduction as in c (0606), it is necessary to prevent the PLL circuit from reacting sensitively to the decrease. Therefore, even when the total signal intensity is reduced from a normal level (0601) free from dirt due to dust or fingerprints and crosses SL2 (0602), it is predetermined from the time of crossing SL2 (point d: 0607). DLY1 (0611), which is a period of, can output the same control signal (eg, “0”) as that of the normal total signal intensity level free from dirt due to dust or fingerprints. Alternatively, DLY1 may not output a control signal. DLY1 is a period during which the total signal intensity can be determined as dirt due to dust or fingerprints when the total signal intensity decreases, and represents a time lag until the total signal intensity actually decreases due to dirt due to dust or fingerprints. However, when the total signal intensity further decreases after crossing SL2 and crosses SL1, as in the fall at b (0605), which is a decrease in the total signal due to the presence of dust or the like, within the period of DLY1 Even so, a control signal (for example, “2”) when dust or the like is present can be output from the time point (point e: 0608) crossing SL1. As a result, in the case of a (0604) or b, which is a decrease in the total signal based on contamination due to fingerprints or the like, an appropriate control signal corresponding to them is sent, but the total signal is within the error range. In the case of c, it is possible to prevent frequent control signals from being output to the PLL circuit. Conversely, when the total signal intensity that once crosses SL1 as in the rise at b turns in the opposite direction and crosses SL1 again, from the time (f point: 0609) that crosses SL1 again, DLY2 (0612) During the period, a control signal (for example, “0”) when dust or the like exists can be extended and output. Here, DLY2 refers to a general period that will be required from the point f until the normal total signal intensity level (0601) free from dirt due to dust or fingerprints. By setting such an extension time, it is possible to secure a time until the total signal intensity level returns to a substantially original level without any abnormality after passing through an area where dust or the like exists, for example.

  <Embodiment 2: Process Flow> FIG. 7 is a flowchart showing an example of the process flow in this embodiment. This embodiment is the same as the total signal acquisition step (S0205) of the first embodiment until the total signal acquisition step (S0705) in which the total signal output in the total signal output step is acquired by the total signal strength information acquisition unit. Omitted because there is. In the present embodiment, the acquired total signal is further sliced at two slice levels depending on the strength by the comparator means of the total signal strength information acquisition unit (total signal strength slice step S0706). Next, the result of the total signal intensity sliced in the total signal intensity slice step is compared to generate a comparator output signal (comparator output signal generation step S0707). Subsequently, the total signal is converted into a ternary signal based on the comparator output signal in the comparator output signal generation step, and total signal strength information is acquired. (Total signal strength information acquisition step S0708). The subsequent steps are the same as those after the control signal acquisition step (S0207) of the first embodiment, and will be omitted.

  <Embodiment 2: Brief Description of Effects> According to the present embodiment, the two slice levels in the comparator means correspond to the total signal level that decreases corresponding to dust on the disk, and dirt caused by fingerprints. By assuming and determining the total signal level to be lowered, it is possible to distinguish the presence of dust or the like on the optical disc from the dirt due to fingerprints and output a control signal corresponding to each to the PLL circuit.

  << Embodiment 3 >>

  <Embodiment 3: Overview> In the optical disk apparatus according to the present embodiment, based on Embodiment 2, the PLL circuit system unit for RF demodulation performs operation hold control of the PLL circuit or gain switching of the PLL circuit based on the total signal strength information. An optical disc apparatus characterized by performing control.

  <Embodiment 3: Configuration> An example of a functional block diagram of the optical disk apparatus in the present embodiment is the same as that in FIG. However, in the case of the present embodiment, as a feature thereof, the PLL circuit of the RF demodulation PLL circuit system unit has a function of performing operation hold control of the RF demodulation PLL circuit or gain switching control of the PLL circuit based on the total signal strength information. Have. “PLL circuit operation hold” is to temporarily stop feedback control of the PLL circuit. “PLL circuit gain switching” means that the gain of the PLL circuit can be controlled by switching to a value other than 0% or 100% by adjusting the value of the output current from the charge pump of the PLL circuit. . By adjusting the value of the output current, an appropriate voltage according to the input RF signal level can be output to the VCO. This makes it possible to prevent a sensitive response of the PLL circuit when the RF signal level is lowered due to dirt such as dust or fingerprints. In the present embodiment, different operation modes can be given to the PLL circuit by the control signal based on the total signal strength information. For example, when the total signal strength information is a ternary signal of “0”, “1”, “2” generated by the “ternarization means”, the control signal based on the total signal strength information “0” is The operation of the PLL circuit may be controlled as a normal gain control signal. In the case of normal gain, the control signal need not be output to the PLL circuit. The control signal based on the total signal strength information “1” may be subjected to PLL circuit gain switching control as a low gain control signal. Specifically, it corresponds to lowering the output current from the charge pump by the control signal. This can prevent a sensitive response of the VCO when the RF signal drops. The gain switching from the low gain to the normal gain may be performed when the control signal “1” is no longer input to the PLL circuit, or the control signal “0” is newly replaced with the control signal “1”. It may be performed when it is input to the PLL circuit. Also, the control signal based on the total signal strength information “2” may be held in the operation of the PLL circuit as a hold control signal. Specifically, the output current from the charge pump is opened by the control signal. Thereby, it is possible to prevent an abnormal response of the VCO when the RF signal is not generated due to dust or the like. The release of the hold may be performed when the control signal “2” is no longer input to the PLL circuit, or instead of the control signal “2”, the control signal “0” is newly input to the PLL circuit. It may be done when.

  <Third Embodiment: Process Flow> FIG. 8 is a flowchart showing an example of the process flow of the RF demodulation PLL circuit system unit in this embodiment. In this embodiment, each step of the optical pickup RF amplifier unit and the total signal intensity acquisition unit, and the control signal acquisition step (S0804) in the RF demodulation PLL circuit system unit are the control signal acquisition step (S0714) of the second embodiment. Since it is the same, it abbreviate | omits. In the present embodiment, the control of the PLL circuit is further determined based on the control signal acquired in the control signal acquisition step (control determination step S0805). First, when the control signal for the operation hold of the PLL circuit is acquired, the operation hold of the PLL circuit is performed (PLL operation hold step S0806). Subsequently, the output current of the charge pump is opened (charge pump output open step S0807). When the gain switching control signal of the PLL circuit is acquired, the output current from the charge pump is switched (output current switching step S0808). Subsequently, a current corresponding to the switching is output from the charge pump (switching current output step S0809). Further, when the total signal strength information is a control signal indicating that there is no normal total signal based on dirt such as dust or fingerprints, or when a control signal from the RF demodulation PLL circuit system unit is not input The current corresponding to the phase difference signal is output from the charge pump (current output step S0810). Since the subsequent steps are the same as those of the second embodiment, the description thereof is omitted.

  <Embodiment 3: Brief Description of Effects> According to the present embodiment, the total signal level that is reduced due to dust or the like and the RF signal that is reduced based on contamination due to fingerprints or the like by holding the PLL circuit or switching the gain. Stable playback can be performed by preventing deterioration of playback performance due to the sensitive response of the PLL circuit according to the level.

  << Embodiment 4 >>

  <Embodiment 4: Overview> The optical disc apparatus of Embodiment 4 is based on Embodiment 1, and converts the total signal from the optical pickup RF amplifier unit into four or more values according to the intensity. The optical disc apparatus is characterized in that the operation of the PLL circuit is performed more variously than the ternary signal by using the signal as total signal intensity information and operating the PLL circuit by a control signal based on the information.

  <Embodiment 4: Configuration> FIG. 9 shows an example of a functional block diagram of an optical disc apparatus according to the present embodiment. The optical disc apparatus according to the present embodiment is based on the first embodiment. Therefore, the description of the same configuration as that of the first embodiment is omitted. In this embodiment, the total signal strength information acquisition unit acquires the second total signal strength information in place of the total signal strength information that is a ternary signal in the first embodiment. The “second total signal strength information” is total signal strength information obtained by converting signals into four or more values according to the strength of the total signal. For example, when the total signal is divided into four according to the intensity, the signal in each area is converted into four values such as “0”, “1”, “2”, “3”, “4”, etc. Applicable. However, the method for dividing the total signal intensity is not a problem.

  <Fourth Embodiment: Process Flow> FIG. 10 is a flowchart showing an example of a process flow in the present embodiment. The processing flow in the present embodiment is based on the processing flow in the first embodiment shown in FIG. Therefore, the description of the processing flow similar to that of the first embodiment is omitted. The feature of this embodiment is that in the total signal acquisition step (S1005), the acquired total signal is converted into an N (N is a natural number of 4 or more) value signal according to the intensity, and second total signal intensity information is acquired ( Second total signal strength information acquisition step S1006). Subsequently, after the step of generating a control signal (control signal generation step S1007) based on the second total signal strength information acquired in the second total signal strength information acquisition step, the control signal generation step of the first embodiment ( S0207) and subsequent steps are the same.

  <Embodiment 4: Effect> In the conventional optical disc apparatus, the operation of the PLL circuit is controlled mainly by the binarized total signal intensity information. By controlling the total signal strength information to a signal having four or more values according to the present invention, the control over the PLL circuit becomes more diverse than in the first embodiment.

It is possible to provide an optical disc apparatus which can deal with various dusts and dirt on the disc and can perform stable reproduction.

Functional block diagram of Embodiment 1 in the present invention The flowchart of Embodiment 1 in this invention Functional block diagram of Embodiment 2 of the present invention Setting of two slice levels in the second embodiment Ternary signal generation in the ternary means of the second embodiment Extension of control signal transmission period in embodiment 2 Flowchart of Embodiment 2 in the present invention Flowchart in the PLL circuit system unit for RF demodulation according to the third embodiment of the present invention. Functional block diagram of Embodiment 4 in the present invention Flowchart of Embodiment 4 in the present invention Functional block diagram of a conventional optical disc apparatus

Explanation of symbols

0101 Optical pickup RF amplifier unit 0102 Total signal strength information acquisition unit 0103 RF demodulation PLL circuit system unit

Claims (4)

Optical pickup RF amplifier,
A total signal strength information acquisition unit that acquires the total signal strength from the optical pickup RF amplifier unit as total signal strength information that is a ternary signal;
An RF demodulation PLL circuit system unit that operates based on the RF signal from the optical pickup RF amplifier unit and the total signal strength information acquired by the total signal strength information acquisition unit;
An optical disc apparatus having The total signal intensity information acquisition unit is configured to slice the total signal from the optical pick RF amplifier unit at two slice levels according to its strength, and to generate respective comparator output signals for the two slice levels;
Ternary means for obtaining the total signal strength information based on comparator output signals for two slice levels generated by the comparator means;
The optical disc apparatus according to claim 1, comprising:   3. The optical disc apparatus according to claim 2, wherein the RF demodulation PLL circuit system unit performs operation hold control of the RF demodulation PLL circuit or gain switching control of the PLL circuit based on the total signal strength information.   The optical disc apparatus according to claim 1, wherein the total signal strength information acquisition unit acquires second total signal strength information that is total signal strength information of four or more values instead of total signal strength information that is a ternary signal.

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