JP6788980B2 - Optical disc playback device, servo control circuit and playback method - Google Patents

Description

The present invention relates to an optical disc player.

Compact discs are widely used as optical disc media for recording various information such as audio data. Grooves called pits are formed on the compact disc, and the patterns of pits and lands represent information.

FIG. 1 is a diagram showing a basic configuration of an optical disc playback device 100R. The optical disc reproduction device 100R includes an optical head 102, a servo mechanism 120, a spindle motor 108, a motor driver 110, an RF amplifier 112, and a reproduction processing circuit 200R.

The optical head 102 irradiates the surface of the optical disc 2 with a laser beam and detects the reflected light. The reflected light has a waveform corresponding to the pattern of lands and pits formed on the surface of the optical disk 2. The optical head 102 includes a plurality of photodetectors that generate electric signals (A signal to F signal) according to the reflected light. The servo mechanism 120 includes a focusing servo, a tracking servo, and a thread servo, and operates based on a drive signal from a servo control circuit built in the reproduction processing circuit 200R. The focusing servo controls the position of the optical head 102 in the height direction of the lens and adjusts the focus. The tracking servo controls the lateral position of the lens and finely adjusts the position of the focus point in the disc surface radial direction so as to follow the pit row. The thread servo slowly moves the entire optical head 102 in the circumferential direction.

The spindle motor 108 rotates the optical disc 2. The motor driver 110 controls the rotation of the spindle motor 108 in response to a control signal from the regeneration processing circuit 200R.

The RF amplifier (pre-servo amplifier) 112 amplifies and processes the electrical signals (A to F signals) obtained from the optical head 102, and performs RF signals, AC (A + C) signals, BD (B + D) signals, and FE (Focus). Generates an Error) signal, TE (Tracking Error) signal, and the like.

Various signals generated by the RF amplifier 112 are input to the reproduction processing circuit 200R. The reproduction processing circuit 200R reproduces data based on the RF signal. Further, a drive signal for controlling the servo mechanism 120 and the motor driver 110 is generated based on the AC signal, BD signal, FE signal, TE signal and the like.

Some of the reproduction processing circuits 200R have an automatic adjustment function of the servo system. For example, the reproduction processing circuit 200R executes automatic adjustment of the servo before the start of reproduction of the optical disk 2, for example, once when the power is turned on. The automatic servo adjustment includes adjustment of the characteristics of the internal filter of the servo system, adjustment of the amplifier offset, adjustment of the gain of the RF amplifier, adjustment of the servo gain, and the like.

Japanese Unexamined Patent Publication No. 2005-92999

In the conventional reproduction processing circuit 200R, if the reproduction environment fluctuates after the automatic adjustment is performed, the parameters obtained by the automatic adjustment become unsuitable and the playability deteriorates.

The present invention has been made in view of the above problems, and one of the exemplary purposes of the embodiment is to provide a reproduction device and a servo control circuit that suppress deterioration of playability due to fluctuations in the reproduction environment. ..

One aspect of the present invention relates to a servo control circuit for an optical disc. The servo control circuit includes a servo filter group including at least one servo filter, an automatic adjustment unit that automatically adjusts the parameters of the servo filter group, and a first signal that reaches a predetermined level when the focus servo is out of sync and when out of synchronization. A trigger circuit for generating a trigger for automatic adjustment by the automatic adjustment unit based on at least one of the second signals at a predetermined level is provided.

When the playback environment fluctuates and the parameters of the current servo filter group become inappropriate, the first signal becomes abnormal due to the focus servo being out of sync, or the second signal becomes abnormal due to the out-of-synchronization. Therefore, by monitoring the first signal or the second signal, it is possible to detect that the parameters of the current servo filter group are inappropriate, and it is possible to perform automatic adjustment again.

The first signal may be an FOK signal obtained by comparing an RF signal based on an electric signal obtained from the pickup with a threshold value.

The trigger circuit may generate a trigger when the number of times the first signal reaches a predetermined level exceeds the first predetermined value within a predetermined time period.

The second signal may be a GFS signal that takes the first level when the synchronization signal of the disk can be correctly detected, and the second level when it is not.

The trigger circuit may generate a trigger when the number of times the second signal reaches a predetermined level exceeds the second predetermined value within a predetermined time period.

When the trigger occurs, the automatic adjustment unit may execute the automatic adjustment after waiting until the next silent portion. Since the automatic adjustment requires a certain amount of time that can be perceived by humans, it is possible to prevent the sound from being interrupted by the automatic adjustment by waiting until the silent part.

The servo filter group may include a focus servo filter. The automatic adjustment unit has an offset amount AC_OFS for the AC signal input to the focus servo filter, an offset amount BD_OFS for the BD signal input to the focus servo filter, an offset amount FD_OFS for the difference signal between the AC signal and the BD signal, and the focus. The overall gain FG of the servo filter may be automatically adjusted.

The servo filter group may include a tracking servo filter. The automatic adjustment unit tracks the offset amount E_OFS for the E signal input to the tracking servo filter, the offset amount F_OFS for the F signal input to the tracking servo filter, the offset amount TD_OFS for the difference signal between the E signal and the F signal, and the tracking. The overall gain TG of the servo filter may be automatically adjusted.

The servo filter group may include a thread servo filter. The automatic adjustment unit may automatically adjust the offset amount SD_OFS with respect to the input signal of the thread servo filter and the overall gain SG of the thread servo filter.

The reproduction control circuit may be integrally integrated on one semiconductor substrate. "Integrated integration" includes cases where all the components of a circuit are formed on a semiconductor substrate or cases where the main components of a circuit are integrated integrally, and some of them are used for adjusting circuit constants. A resistor, a capacitor, or the like may be provided outside the semiconductor substrate. By integrating the circuits on one chip, the circuit area can be reduced and the characteristics of the circuit elements can be kept uniform.

Another aspect of the present invention relates to an optical disc playback device. The playback device includes a pickup and a lens, a servo mechanism for positioning the pickup and the lens, a preservo amplifier for processing a signal from the pickup, and any of the above servos for controlling the servo mechanism based on the signal from the preservo amplifier. It includes a control circuit.

It should be noted that any combination of the above components and those in which the components and expressions of the present invention are mutually replaced between methods, devices, systems and the like are also effective as aspects of the present invention.

According to an aspect of the present invention, deterioration of playability due to changes in the reproduction environment can be suppressed.

It is a figure which shows the basic structure of the optical disk reproduction apparatus. It is a block diagram of the optical disk reproduction apparatus which includes the servo control circuit which concerns on embodiment. It is a circuit block diagram of a focus servo filter. It is a circuit block diagram of a tracking servo filter. It is a circuit block diagram of a thread servo filter.

Hereinafter, the present invention will be described with reference to the drawings based on preferred embodiments. The same or equivalent components, members, and processes shown in the drawings shall be designated by the same reference numerals, and redundant description will be omitted as appropriate. Further, the embodiment is not limited to the invention but is an example, and all the features and combinations thereof described in the embodiment are not necessarily essential to the invention.

FIG. 2 is a block diagram of an optical disc reproduction device 100 including the servo control circuit 300 according to the embodiment. The optical disc playback device 100 reads the audio data recorded on the optical disc (compact disc) 2 and reproduces the audio data.

The optical disc reproduction device 100 includes an optical head 102, a servo mechanism 120, a spindle motor 108, a motor driver 110, and a reproduction processing circuit 200.

The optical head 102 includes a pickup 104 and a lens 106. The optical head 102 irradiates the surface of the optical disk 2 with laser light from a laser (not shown) and detects the reflected light. The reflected light has a waveform corresponding to the pattern of lands and pits formed on the surface of the optical disk 2. The pickup 104 is divided into six regions called A to F, and a photo detector is provided for each region. A signal to F signal are generated by a plurality of photodetectors.

The servo mechanism 120 includes a thread servo 122, a focusing servo 124, and a tracking servo 126. It operates based on the drive signals SD (Sled Drive), FD (Focus Drive), and TD (Tracking Drive) from the servo control circuit 300 built in the reproduction processing circuit 200.

The focusing servo 124 controls the position of the optical head 102 in the height direction of the lens 106 and adjusts the focus. The tracking servo 126 controls the lateral position of the lens 106 and finely adjusts the position of the focus point in the disc surface radial direction so as to follow the pit row. The thread servo 122 slowly moves the entire optical head 102 in the circumferential direction.

The spindle motor 108 rotates the optical disc 2. The motor driver 110 controls the rotation of the spindle motor 108 in response to a control signal from the regeneration processing circuit 200.

The reproduction processing circuit 200 includes a pre-servo amplifier 202, a binarization circuit 204, an EFM demodulator 206, and a servo control circuit 300. The reproduction processing circuit 200 is a functional IC integrally integrated on one semiconductor substrate, or is a module. The pre-servo amplifier 202 may be an IC different from the reproduction processing circuit 200. The reproduction processing circuit 200 may be configured by a digital circuit, or may be configured by a combination of a digital circuit and an analog circuit.

The pre-servo amplifier 202 corresponds to the RF amplifier 112 in FIG. The pre-servo amplifier 202 amplifies the sum of the A signal to the D signal to generate an RF signal. The pre-servo amplifier 202 may include an AGC (Automatic Gain Controller) whose gain is automatically adjusted in order to optimize the amplitude of the RF signal.

The pre-servo amplifier 202 also generates an AC signal and a BD signal. The AC signal is the sum of the A signal and the C signal, and the BD signal is the sum of the B signal and the D signal.

The binarization circuit 204 compares the RF signal with the threshold value and generates an EFM signal having a high level and a low level according to the comparison result. The EFM demodulator 206 demodulates the EFM signal. An ECC circuit or the like is built in the subsequent stage of the EFM demodulator 206, but it is omitted here.

The servo control circuit 300 generates an SD signal, an FD signal, and a TD signal based on an AC signal, a BD signal, an E signal, an F signal, and the like, and controls the servo mechanism 120. The servo control circuit 300 includes a servo filter group 302, an automatic adjustment unit 304, a trigger circuit 306, a synchronization detection circuit 308, and a FOK circuit 310.

The servo filter group 302 includes at least one servo filter. In this embodiment, a focus servo filter, a tracking servo filter, and a thread servo filter are provided as described later.

The automatic adjustment unit 304 automatically adjusts the parameters of the servo filter group 302.

The trigger circuit 306 is a trigger S13 for automatic adjustment by the automatic adjustment unit 304 based on at least one of a first signal S11 that becomes a predetermined level when the focus servo is out of sync and a second signal S12 that becomes a predetermined level when out of synchronization. Occurs.

The FOK circuit 310 generates a FOK (Focus OK) signal by comparing the RF signal with the threshold value. In the out-of-focus servo state where the servo does not follow well, the RF signal tends to maintain a constant low level or high level. On the other hand, when the servo condition is good, the FOK signal frequently transitions to the low level according to the pit and land patterns. The FOK signal is suitable as the first signal S11.

The synchronization detection circuit 308 generates a GFS signal that takes the first level when the synchronization signal of the disk can be correctly detected and the second level when it cannot be detected correctly. This GFS signal is suitable as the second signal S12.

The trigger circuit 306 generates an automatic adjustment trigger S13 when the number of times the first signal S11 reaches a predetermined level exceeds the first predetermined value X within a predetermined time period τ ₁ . Further, the trigger circuit 306 generates the trigger S13 when the number of times the second signal S12 reaches the predetermined level exceeds the second predetermined value Y within the predetermined time period τ ₂ . Note that τ ₁ and τ ₂ may be equal or different. Further, the predetermined values X and Y may be equal or different.

When the trigger S13 is generated, the automatic adjustment unit 304 preferably executes automatic adjustment after waiting until the next silent portion. Since the automatic adjustment requires a certain amount of time that can be perceived by humans, it is possible to prevent the sound from being interrupted by the automatic adjustment by waiting until the silent part.

FIG. 3 is a circuit block diagram of the focus servo filter 350. The focus servo filter 350 includes some adders 352, some filters (F-LPS, F-LPF, F-BPF), noise shaper NS, and amplifiers (coefficient circuits) (FB_AG, FB_BD, FTG, OSCG, FG). , FHIG, FSG, FLG, FHG), and selector SEL. The configuration of the focus servo filter 350 is not particularly limited, and may be another known configuration. Since the configuration and operation of each component are known, the description thereof will be omitted. The state of each selector SEL can be controlled based on the value of the corresponding register. The focus servo filter 350 generates a focus drive control signal (FDOUT) based on the AC signal and the BD signal. The FDOUT signal corresponds to the FD signal of FIG.

The f_loop signal is used for on / off control of the focus loop. The gairan signal is a disturbance signal for automatic adjustment, and is generated by the automatic adjustment unit 304. OSCG is a gain for setting the disturbance level for automatic adjustment. The f_gairan_on signal is used to switch the selection of the gairan signal. The f_search signal is a focus search signal. The fmuto signal is a signal for turning off the focus loop.

F-LPS is a lag lead filter. The F-BPF is a bandpass filter composed of a combination of a lowpass filter (LPF) and a highpass filter (HPF). The F-LPF is a servo band filter.

Only the functions related to the present invention will be described in detail. In this focus servo filter 350, the offset amount AC_OFS with respect to the AC signal, the offset amount BD_OFS with respect to the BD signal, the offset amount FD_OFS with respect to the difference signal S14 between the AC signal and the BD signal, and the overall gain FG of the focus servo filter are automatically set. It is the target of automatic adjustment by the adjustment unit 304. Other parameters may be fixed values or set values by registers.

FIG. 4 is a circuit block diagram of the tracking servo filter 360. The tracking servo filter 360 also includes some adders 362, some filters (T-LPS, T-LPF, T-BPF, E + F + HPF), noise shaper NS, and amplifiers (TB_E, TB_F, GD_E, GD_F, TTG, OSCG). , TG, THIG, TSG, TLG, THG), and selector SEL. The tracking servo filter 360 generates a tracking drive control signal (TDOUT) based on the E signal and the F signal. The TDOUT signal corresponds to the TD signal of FIG.

E + F + HPF is a filter for E + F signals. The tmuti signal is a signal for turning off the tracking loop. The gairan signal is a disturbance signal for automatic adjustment. The t_gairan_on signal is a control signal of the addition switch for gairan, and is turned on when the tracking gain is measured.

T-LPS is a lag lead filter. The T-BPF is a bandpass filter composed of a combination of a lowpass filter (LPF) and a highpass filter (HPF). The T-LPF is a servo band filter.

The thpfsel, tthrsel signal, thpfoff signal, and tthroff signal are signals for DC hold operation. The jump signal is a signal that is output at the time of track jump. The tmuto signal is a signal for turning off the tracking loop.

In this tracking servo filter 360, the offset amount E_OFS with respect to the E signal, the offset amount F_OFS with respect to the F signal, the offset amount TD_OFS with respect to the difference signal S15 between the E signal and the F signal, and the overall gain TG of the tracking servo filter 360 are formed. It is the target of automatic adjustment by the automatic adjustment unit 304.

FIG. 5 is a circuit block diagram of the thread servo filter 370. The thread servo filter 370 is also composed of a combination of an adder 372, a filter (S-LPS), an amplifier (SG), and a selector SEL. The thread servo filter 370 generates a thread drive control signal (SDOUT) based on the SD_IN signal. The SDOUT signal corresponds to the SD signal of FIG. The SD_IN signal is the output data of the low-pass filter (T-LPF) of the tracking servo filter 360 of FIG.

The smoothie signal is a signal for turning off the thread loop. The sled_h and sled_l signals are output values selected during thread move and multitrack jump. The thread_sel signal is a thread servo control signal.

In this thread servo filter 370, the offset amount SD_OFS with respect to the input signal SD_IN of the thread servo filter 370 and the overall gain SG of the thread servo filter 370 are the targets of automatic adjustment by the automatic adjustment unit 304.

The above is the configuration of the optical disc playback device 100 according to the embodiment. According to the optical disc playback device 100, when the playback environment fluctuates and the parameters of the current servo filter group 302 become inappropriate, the first signal S11 becomes abnormal due to the focus servo being out of focus, or the first signal S11 is out of synchronization. The second signal S12 becomes abnormal. Therefore, by monitoring the first signal S11 and / or the second signal S12, it is possible to detect that the parameters of the current servo filter group 302 are inappropriate, and it is possible to perform automatic adjustment again. As a result, deterioration of playability due to changes in the playback environment can be suppressed or improved.

The present invention has been described above based on the embodiments. This embodiment is an example, and it will be understood by those skilled in the art that various modifications are possible for each of these components and combinations of each processing process, and that such modifications are also within the scope of the present invention. is there. Hereinafter, such a modification will be described.

In the embodiment, a compact disc is taken as an example, but the present invention is not limited thereto, and can be applied to various similar optical disc playback devices.

In the embodiment, a plurality of servo filters are automatically adjusted all at once based on the first signal S11 or the second signal S12, but the present invention is not limited thereto. For example, when the trigger S13 based on the first signal S11 is generated, the servo filter (for example, the focus servo filter) that affects the focus servo out of focus is automatically adjusted, and when the trigger S13 based on the second signal S12 is generated. May perform automatic adjustment of servo filters (eg thread servo filters, tracking servo filters) that affect synchronization. As a result, the time required for automatic adjustment can be shortened as compared with the case where all filters are subject to automatic adjustment.

Further, in addition to the servo filter, the automatic adjustment unit 304 may target the gain of the VCO (Voltage Controlled Oscillator) or the RF amplifier for automatic adjustment.

Although the present invention has been described using specific terms based on the embodiments, the embodiments merely indicate the principles and applications of the present invention, and the embodiments are defined in the claims. Many modifications and arrangement changes are permitted without departing from the ideas of the present invention.

2 ... Optical disk, 100 ... Optical disk player, 102 ... Optical head, 104 ... Pickup, 106 ... Lens, 108 ... Spindle motor, 110 ... Motor driver, 112 ... RF amplifier, 120 ... Servo mechanism, 122 ... Thread servo, 124 ... Focusing servo, 126 ... Tracking servo, 200 ... Reproduction processing circuit, 202 ... Preservo amplifier, 204 ... 2 binarization circuit, 206 ... EFM demodulator, 300 ... Servo control circuit, 302 ... Servo filter group, 304 ... Automatic adjustment Part, 306 ... Trigger circuit, 308 ... Synchronous detection circuit, 310 ... FOK circuit, 350 ... Focus servo filter, 352 ... Adder, 360 ... Tracking servo filter, 362 ... Adder, 370 ... Thread servo filter, 372 ... Adder ..

Claims (18)

A group of servo filters including at least one servo filter,
An automatic adjustment unit that automatically adjusts the parameters of the servo filter group,
A trigger circuit that generates a trigger for the automatic adjustment by the automatic adjustment unit based on at least one of a first signal that becomes a predetermined level when the focus servo is out of focus and a second signal that becomes a predetermined level when the synchronization is out of sync.
With
The servo filter group includes a thread servo filter.
The thread servo filter is
The first selector that receives the input signal and the value 0 and selects one according to the mute selection signal,
An adder that adds the output of the first selector and the offset amount SD_OFS,
A low-pass filter that receives the output of the adder,
An amplifier that amplifies the output of the low-pass filter with a gain SG,
A second selector that receives the output of the amplifier, the value sled_h used at the time of thread move, the value sled_l and the value 0 used at the time of multi-track jump, and selects one according to the control signal thread_sel of the thread servo.
Is included , and the output of the second selector is output as a thread drive control signal.
The automatic adjustment unit
And the offset amount SD_OFS of the sled servo filter,
The gain SG of the thread servo filter and
Servo control circuit characterized by automatic adjustment. The servo control circuit according to claim 1, wherein the first signal is an FOK signal obtained by comparing an RF signal based on an electric signal obtained from a pickup with a threshold value. The trigger circuit according to claim 2, wherein the trigger circuit generates the trigger when the number of times the first signal reaches the predetermined level exceeds the first predetermined value within a predetermined time period. Servo control circuit. The second signal according to any one of claims 1 to 3, wherein the second signal is a GFS signal that takes the first level when the synchronization signal of the disk can be correctly detected and the second level when the synchronization signal of the disk is not detected correctly. Servo control circuit. The fourth aspect of the present invention, wherein the trigger circuit generates the trigger when the number of times the second signal reaches the predetermined level exceeds the second predetermined value within a predetermined time period. Servo control circuit. The servo control circuit according to any one of claims 1 to 5, wherein when the trigger is generated, the automatic adjustment unit waits until the next silent portion and then executes the automatic adjustment. In the servo control circuit, the six photodetectors included in the optical head are from a pre-servo amplifier that processes electrical signals A to F signals, AC signal that is the sum of A signal and C signal, and B signal and D. The servo control circuit according to any one of claims 1 to 6, wherein a BD signal, an E signal, and an F signal, which are sums of signals, are input. The servo filter group generates a focus drive control signal based on the AC signal and the BD signal. Including focus servo filter
The automatic adjustment unit
The offset amount AC_OFS with respect to the AC signal and
The offset amount BD_OFS with respect to the BD signal and
The offset amount FD_OFS with respect to the difference signal between the AC signal and the BD signal, and
The overall gain FG of the focus servo filter and
The servo control circuit according to claim 7, wherein the servo control circuit is automatically adjusted. The servo filter group includes a tracking servo filter that generates a tracking drive control signal based on the E signal and the F signal.
The automatic adjustment unit
The offset amount E_OFS with respect to the E signal and
The offset amount F_OFS with respect to the F signal and
The offset amount TD_OFS with respect to the difference signal between the E signal and the F signal, and
The overall gain TG of the tracking servo filter and
The servo control circuit according to claim 7, wherein the servo control circuit is automatically adjusted. The servo control circuit according to any one of claims 1 to 9, wherein the automatic adjustment unit adjusts the gain of the RF amplifier. The servo control circuit according to any one of claims 1 to 10, wherein the servo control circuit is integrally integrated on one semiconductor substrate. With an optical head, including a pickup and lens,
A servo mechanism for positioning the optical head and the lens, and
A pre-servo amplifier that processes the signal from the pickup, and
The servo control circuit according to any one of claims 1 to 11, which controls the servo mechanism based on a signal from the pre-servo amplifier.
An optical disc playback device characterized by the above. It is a method of playing optical discs.
A step to generate a first signal that reaches a predetermined level when the focus servo is out of focus,
A step to generate a second signal that reaches a predetermined level when out of sync,
A step of generating a trigger signal based on at least one of the first signal and the second signal.
A step of automatically adjusting the parameters of the servo filter group including at least one servo filter, triggered by the trigger signal, and
With
The servo filter group includes a thread servo filter.
The processing of the thread servo filter is
An input selection step that selects one of the input signal and the value 0 according to the mute selection signal, and
An offset step that adds an offset amount SD_OFS to the signal selected in the input selection step, and an offset step.
A low-pass step for extracting the low-frequency component of the signal obtained in the offset step, and
An amplification step that amplifies the signal obtained in the low-pass step with a gain SG,
With the output selection step of selecting one of the signal obtained in the amplification step, the value sled_h used at the time of thread move, the value sled_l used at the time of multitrack jump, and the value 0 according to the control signal thread_sel of the thread servo. ,
A step of outputting the signal selected in the output selection step as a thread drive control signal, and
It includes,
The step of performing the automatic adjustment is
The offset amount SD_OFS of the thread servo filter and
The gain SG of the thread servo filter and
A playback method characterized by automatically adjusting. The reproduction method according to claim 13, wherein the first signal is an FOK signal obtained by comparing an RF signal based on an electric signal obtained from a pickup with a threshold value. The reproduction method according to claim 13, wherein the trigger signal is generated when the number of times the first signal reaches the predetermined level exceeds the first predetermined value within a predetermined time period. The second signal according to any one of claims 13 to 15, wherein the second signal is a GFS signal that takes the first level when the synchronization signal of the disk can be correctly detected and the second level when it is not. How to play. The reproduction method according to claim 16, wherein when the number of times the second signal reaches the predetermined level exceeds the second predetermined value within a predetermined time period, the trigger signal is generated. The reproduction method according to any one of claims 13 to 17, wherein the automatic adjustment is executed after waiting for the next silent portion after the generation of the trigger signal.

Images