JPS6171425A - Recording disc information reproducing device - Google Patents

Abstract

PURPOSE:To improve the error rate more by biasing an information read spot in track tangential direction of a recording disc based on a synchronizing signal included in a reproduced high frequency signal so as to eliminate jitter in a reproduced digital signal without incurring increase in the memory capacity. CONSTITUTION:An output of an adder 51 drives a spindle motor 1l for driving LDD, LD circuits via equalizer amplifiers 52, 53 and a driver 54. This is the spindle servo system. Further, an output of the equalizer amplifier 52 drives an actuator (not shown in figure) incorporated in a pickup 12 via a loop switch 55, a changeover switch 56 and a driver 57. The driving of the actuator biases the light spot for reading information in the recording track tangential direction of the disc. This is the tangential servo system. Since the said tangential servo system is adopted in addition to the spindle servo system and a time axis servo using a buffer memory, jitter is suppressed to a degree before the stage of the buffer memory.

Description

TECHNICAL FIELD The present invention relates to a recording disc information reproducing apparatus, and more particularly to a reproducing apparatus for reproducing recorded information on a recording disc on which digital signals are recorded.

BACKGROUND ART As a recording disk on which digital signals are recorded, audio signals are subjected to predetermined digital modulation 5I! l! A so-called compact disc (hereinafter referred to as CD), which is a digital audio disc that is processed and recorded in the form of a pulse train, is known. A method of duplicating and recording a pulse train signal that is digitized using a modulation method (Japanese Patent Application No. 58-45)
780 Akira MRA)) video disc (hereinafter referred to as L
(abbreviated as DD) has been developed.

In this recording system, the audio signal is converted into two channels, and the 2.3 MHz and 2.8 MH2 audio carriers are each FM-modulated by two audio channel signals. In addition, the video signal has a sync chip of 7°6MH2 and a pedestal level of 8.
．． 1M1-1z, the frequency is converted so that the white beak becomes 9.3MtIZ. Then, the audio signal is further converted into PCM (Pulse Code Modulus).
The signal is digitized and converted into a pulse train signal using a modulation method such as .

This pulse train signal is, for example, an EFM (Eight to
The signal is suitable for recording using the l"ourtechn MODTLATION) method, and the frequency spectrum is a frequency component of a pulse train having a width of 3T to 11T. Here, T indicates the pit period of the PCM signal, and 3 The pulse of Ding is about 720KHz, the maximum width is 1
The 1T pulse has a frequency of about 200KHz. Such a pulse train signal is about 1/1 of the video main carrier.
i! at a level below 0! The signal is then slice-amplified near the zero-crossing point to become a pulse-width modulated signal, which is used as a recording signal.

The frequency spectrum of an RF (high frequency) signal emitted from a recording disk on which a video signal and an audio signal are recorded by the above recording method is as shown in FIG. In Figure 1, the component indicated by A is the digitized audio signal component, and the component indicated by B is the audio FM.
The signal component indicated by C is the color information component in the video FM signal, and the component not indicated by D is the luminance information component in the video FM signal.

Since the dynamic range of the digitized audio signal can be approximately 90 dB or more, the sound quality can be significantly improved compared to recording and reproducing audio signals using the FM modulation method.

By the way, in a general demodulating device for a PCM digital signal in a CD playback device, the read clock is fixed,
On the other hand, by phase-synchronizing the rotation of the recording disk and reading out the information once stored in the memory using an interrupt clock synchronized with the reproduction clock signal, in synchronization with the continuous output clock, jitter, which is a component of time axis variation, can be eliminated. It is configured to be removed.

However, such time-base servo alone cannot necessarily suppress jitter sufficiently, and further improvement of the error rate is desired. Furthermore, if the jitter is large at the time axis servo stage, the stored data will always remain in the memory, so it is necessary to increase the memory capacity accordingly.

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned points, and provides a recording disk information reproducing device that can remove jitter from a reproduced digital signal without increasing memory capacity and further improve error rate. The purpose is to

A recording disc information reproducing apparatus according to the present invention includes a demodulating means for demodulating a digital signal included in a reproduced high-frequency signal;
a first control system that controls the rotational speed of the recording disk according to the phase difference between the reproduced clock signal and the fixed reference clock signal included in the reproduced digital signal; A recording disc information reproducing device comprising: a second control system that reads stored information from the memory in synchronization with the memory and does not read stored information from the memory in synchronization with a constant continuous output clock signal; The present invention is characterized in that it includes a third control system that biases the single report reading spot in the track tangential direction of the recording disk based on a synchronization signal included in the high-frequency signal.

Friend-LJL Hereinafter, embodiments of the present invention will be described in detail based on the drawings.

FIG. 2 is a block diagram showing an embodiment of a recording disc information reproducing apparatus according to the present invention. Such a playback device is a CD
This is a so-called compatible play 1 that can also play back ordinary video discs (hereinafter abbreviated as LD) on which video signals and audio signals are frequency-modulated and recorded. As mentioned above, since the playback speed is different between video discs (LD, LDD) and digital audio discs (CD), this player has a spindle motor 1 for driving the LD and LDD and a spindle motor 2 for driving the CD rotation. is provided. These spindle motors 1.2 are selected depending on the type of disc to be reproduced, and are switched by a switching mechanism 4 using, for example, a motor 3 as a driving source.

In order to detect the disc size of the disc 5 to be reproduced, for example, three detection sensors 6, 7 and 8 are provided corresponding to the disc size in the disc radial direction. The disc size for CDs is approximately 5 inches (1
2cn+), and in the case of video discs (LD, LDD), there are two types of outer diameters: 8 inches and 12 inches. The outputs of the three detection sensors 6 , 7 and 8 are waveform-shaped by a waveform shaping circuit 9 and then supplied to a disk discrimination circuit 10 . As the detection sensor, for example, an optical sensor is used, but the detection sensor is not limited to this.

The disc discrimination circuit 10 determines whether the disc to be played is a CD or LD based on the detection outputs of the detection sensors 6.7 and 8.
It is determined which of the three types of disks D and LD it is. A specific circuit configuration of this disk discrimination circuit 10 is shown in FIG. In this figure, in the case of CD, the disc size is determined to be the minimum (12 cm), and the detection output of the innermost detection sensor 6 and the inverter 79
．． The output of the AND gate circuit 78 which converts the inverted output of the detection sensor 7.8 which has passed through the detection sensor 80 into three-man power becomes the CD discrimination information.

That is, the detection sensor 6 is on, and the other detection sensors 7.
8 is off, it is determined to be a CD. In the case of a video disc, since the disc sizes are 8 inches and 12 inches, the detection output of the detection sensor 7 or 8 passes through the OR gate circuit 69 and becomes the output of the AND gate circuits 70 and 71, respectively. In addition, a frame synchronization detection circuit 2 to be described later
A frame synchronization detection signal generated when a frame synchronization signal is detected from 1 becomes the external power of the AND gate circuit 71, and is also inverted by the inverter 72 and becomes the external power of the AND gate circuit 70. and detection sensor 7 or 8
When a detection output is generated and a frame synchronization detection signal is input, the AND gate circuit 71 outputs LDD discrimination information, and when the frame synchronization detection signal is not input, the AND gate circuit 70 outputs LD discrimination information. . This discrimination information is used to drive an indicator 11 that displays the type of disc, and as a switching signal for various switches to be described later.

A pickup 12 for reading recorded information from the disk 5 is supported by a slider base (not shown)' which is movably provided in the radial direction of the disk 5, and the slider base is composed of a slider motor, a reduction gear, etc. It is driven by a drive afS (not shown). Read information read from the recording disk 5 by the pickup 12 is supplied to a digital information demodulation system 14, an analog audio demodulation system 15, and a video demodulation system 16 through an RF amplifier 13, respectively. RF amplifier 1
3 has a wide band of about 5 KHz to 14 MHz, and a single amplifier can amplify a reproduced PCM audio signal, a reproduced FM audio signal, and a reproduced video signal.

The digital information demodulation system 14 is provided with a changeover switch 17 that changes depending on the type of disc to be reproduced.
Based on the disc information from , it switches to the a side in the case of an LDD, and to the a side in the case of a CD. That is, L.D.D.
The signal processing system for the reproduced digital signal is switched between reproduction and CD reproduction. During CD playback, the playback RF output contains PCM audio information, and this PCM audio information is converted into an MTF (ModulaNonT
transfer) compensation is applied.

On the other hand, in the case of LDD, FM audio information and FM
PCM Δ-dio information included in the reproduced RF signal together with the video information is extracted by an LPF (low pass filter) 19 and supplied to the DI 7122 circuit 20 . PCM
Audio information is, for example, an EFM signal, but if the digital signal is directly superimposed on an FM-modulated video signal during recording, the digital signal component will be interfered with by the low-frequency component of the FM video signal. , the low frequency components are boosted and recorded. Therefore, during reproduction, the de-emphasis circuit 2o performs compensation by dropping the low-frequency components boosted during recording. This makes it possible to improve the 8'/N ratio of the digital signal against low frequency noise during recording and reproduction.

Note that instead of switching the signal processing system using the changeover switch 17, the power supply to each signal processing system circuit is set to 0N.
Even if it is set to 10FF, the same effect can be obtained by 1q.

The reproduced EFM signal that has passed through the changeover switch 17 is supplied to the EFM demodulation circuit 22 via the frame synchronization detection circuit 21 and is also supplied to the reproduced clock extraction circuit 23. The EFM demodulation circuit 22 demodulates the signal into a PCM digital signal.

This demodulated signal is sent to the memory 24 such as RAM (random access memory) 1Illt2 of the memory controller 25.
tl, but at this time, the memory controller 25 performs writing in synchronization with the square clock, which is the frequency-divided output from the frequency divider 26 of the reproduced clock.

Reading of stored information from the memory 24 is performed in synchronization with a read clock obtained by dividing the oscillation output of a VC○ (voltage control excavator) 27 in a PLL (phase locked loop) circuit by a frequency divider 28. It has become so. The PLL circuit is the VCO27 mentioned above.
, the frequency division output of the reproduced clock by the frequency divider 29 and the VCO2
A phase comparator (P/C) 31 which uses the divided output from the frequency divider 27 of the oscillation output of 7, an LPF (low pass filter) 32 which receives this comparison output as input, and this L P
It is constituted by a changeover switch 33 that selectively supplies the output voltage of F 32 and the reference voltage VrQf+ to the VCO 27.

In the PLL circuit, the change-over switch 33 is set to the a side during LDD playback and switches the output voltage of the LPF 32 to the output voltage of the LPF 32 during LDD playback, and switches to the b side during CD playback to set the reference voltage Vrer to the VCO.
Supply to 27. As a result, during LDD playback, the read clock for reading stored information from the memory 24 is set to P.
The phase of the reproduced clock is synchronized by the LL circuit, and when the loop switch 59, which will be described later, is turned on (closed) during CD playback, the output of the phase comparator 31 becomes LP.
By driving the spindle motor 2 for driving the CD rotation through F77, the reproduced clock is phase-synchronized with the fixed clock obtained by the VCO 27 whose bias is in a fixed state.

The digital signal thus read out is converted into an analog audio signal by a D/A (digital/analog) converter 34, and then sent to an LPF 35L.

Left and right playback audio outputs are provided via 35R.

The usage status in the memory 24 is constantly monitored by the memory controller 25, and when the memory 24 overflows or becomes blank (no data), the controller 25 sends information indicating these statuses to the voltage generator 3.
Supply to 6. During LDD regeneration, this voltage generator 36
generates a positive control voltage when the memory 24 overflows, and generates a negative control voltage when the memory 24 becomes blank, according to information indicating the usage status of the memory 24 from the memory controller 25. , the frequency of the read clock is controlled by superimposing it on the output voltage of the LPF 32 and supplying it to the VCO 27 via the changeover switch 33.

In this way, the amount of data stored in the memory 24 is constantly monitored, and when there is an excess or deficiency in the capacity and processing capacity of the memory 24, a positive or negative control voltage is generated to request the PLL circuit to take action. By doing so, the memory 24 can always be maintained in a normal state.

In the analog audio demodulation system 15, 2,3M) (Z and 2.8MH7 A'-
The output of the BPF (band pass filter) 371.37R that passes only the diocarrier component is [M demodulator 38
The signal is FM demodulated in L and 38R, and becomes left and right playback audio outputs via de-emphasis circuits 39L and 39R.

In the video demodulation system 16, only video information is extracted from the reproduced RF signal by a BPF & notch circuit 40. This BP
In the F&notch circuit 40, the EFM component and 2.3MHz, 2.8MHz included in the reproduced RF signal during LDD reproduction
The audio carrier component of z is actively removed. This extracted information is supplied to the FM demodulator 42 via the limiter circuit 41 and is FM demodulated. This demodulated output is sent to a dropout compensator (DQC) via an LPF43.
) 44, and dropout correction is performed in the compensator 44. This dropout compensator 44 is, for example, an analog switch that is turned off by the detection output of a dropout sensor (008) 46 that detects a dropout based on a reproduced RF signal supplied via an HPF (bypass filter) 45. and a hold capacitor provided between this switch output end and a reference potential point. Therefore, when a dropout occurs, the level of the output of the LPF 43 immediately before the output of the dropout sensor 46 is held and sent to the next stage circuit, thereby performing dropout compensation. The output of this dropout compensator 44 becomes one video output.

The output of the dropout compensator 44 is sent to the horizontal sync separation circuit 4.
7, and the horizontal synchronizing signal is separated and output. This horizontal synchronizing signal is supplied to phase comparators 48 and 49, and a phase match with the reference signal output from the reference signal generator 50 is detected. The output of the phase comparator 48 is supplied to the amplifier 51, and the output of the phase comparator 49 is supplied to the equalizer amplifier 5.
It serves as another input to the adder 51 via 2. The output of the adder 51 is the equalizer amplifier 53 and the driver 5.
The spindle motor 1 for driving the LOD and LD rotations is driven through the motor 1111. This is the spindle servo system. In addition, the output of the equalizer amplifier 52 is connected to the loop switch 5.
5. The actuator built into the pickup 12 (uf
) to drive.

By driving this actuator, a light spot for reading information is biased in the tangential direction of the recording track of the disk. This is the tandiencialmibo group. Note that the actuator may be a tangential mirror that rotates to tilt the optical spot for reading information in the direction tangential to the recording track of the disk, or a tangential mirror that rotates to tilt the optical spot for reading information in the direction tangential to the recording track of the disk. A configuration may also be used in which the optical spot for information reading is shifted in the tangential direction of the recording track of the disk by displacement.

The loop switch 55 is turned on (closed) in response to a spindle lock signal output from the spindle lock detection circuit 58 when locking of the spindle servo system is substantially completed. That is, at the start of reproduction, the spindle motor 1 is first driven by the output of the phase comparator 48 to perform rough adjustment of the time axis (spindle servo),
When the locking of the spindle servo is substantially completed, the loop switch 55 is turned on, the actuator is driven by the output of the phase comparator 49, and W adjustment (tangential mebo) on the time axis is performed.

According to this, residual jitter components that cannot be removed by the spindle servo system can be removed by the tangential servo system.

However, even in the tangential servo system, jitter cannot be completely removed because a mechanical system such as an actuator drive vJ mechanism cannot sufficiently follow the high-frequency component of residual jitter. Therefore, in the digital information demodulation system 14 mentioned above, P
By setting the cutoff frequency of the LPF 32 of the LL circuit lower than the maximum frequency of the band of the tangential servo lube to cut the high frequency component of residual jitter,
This means that residual jitter components can be removed. More preferably, by setting the cutoff frequency of the LPF 32 lower than the disk eccentricity frequency (30 to 8 Hz in the case of LDD), it is possible to completely eliminate jitter caused by disk eccentricity.

Although the spindle servo and tangential servo are performed based on the horizontal synchronization signal, similar effects can be obtained by performing the spindle servo and tangential servo based on the 3.58 MHz color subcarrier included in the reproduced FM video signal.

The above is a servo system when reproducing a video disc (+-DO, LD), but when reproducing a CD, spindle servo is performed based on the output of the phase comparator 31 in the digital information demodulation system 14 described above. That is, the output of the phase comparator 31 drives the spindle motor 2 for driving the CD rotation via the loop switch 59 and the driver 60, which are turned on (open) during CD reproduction. Conventionally, the above-mentioned tangential servo was not performed during CD playback, but since the spindle motor 2 cannot sufficiently follow the high frequency component of the output signal of the phase comparator 31, which is a time axis error signal, this In the example, HPF
A servo, that is, a tangential servo, in which the high frequency component of the time axis error signal extracted by the time axis error signal 61 drives the actuator in the pickup 12 via the changeover switch 56 and the driver 57 is also employed. The changeover switch 56 is set to the a side when playing an LDD or LD, and to the b side when playing a CD, based on the discrimination result of the disc discrimination circuit 10.
Switch to the side.

Incidentally, during CD playback, the mechanical servo is performed based on the divided output of the reproduced clock extracted by the reproduced clock extraction circuit 23, but the frame synchronization signal detected by the frame synchronization detection circuit 21 Even if it is performed based on the frequency-divided output of , the same effect can be obtained since the frame synchronization signal and the reproduced clock are in the same period and relationship.

The output of the spindle lock detection circuit 58 is connected to the inverter 62.
This signal is inverted and becomes the sole power of the OR gate circuit 63 as a spindle unlock signal indicating that the spindle servo system is not in the locked state.

As the output of the OR gate circuit 63, a random access report signal generated at the time of a random access command such as scan, search, jump, etc. is supplied. Furthermore, the LDD information output from the disk discrimination circuit 10 is also input to the OR gate circuit 63.

The output of the OR gate circuit 63 is supplied to the recovered clock extraction circuit 23 via the control command circuit 64.

A specific circuit configuration of the recovered clock extraction circuit 23 is shown in FIG. In this figure, the reproduced EFM signal is transmitted to the phase comparator 6.
5, the phase difference with the oscillation output of the VCO (voltage! IJ control oscillator) 66 is detected, and the phase difference signal is sent to the LPF 67.
and is supplied to the VCO 66 via the changeover switch 68. As described above, a PLL circuit that generates a reproduced clock is configured.

The changeover switch 68 is normally located on the a side and supplies the output of the LPF 67 to the VCO 66, but the control command circuit 6 described above
When a command signal is output from 4, it switches to the b side in response to this command signal and supplies a predetermined base lightning pressure Vraf2 to the VCO 66.

That is, when the spindle servo is not in a locked state or when the information reading optical spot jumps tracks due to a random access command such as scan, search, or jump, the base voltage vref2 is applied to the VCO 66 to change its oscillation frequency. By fixing the frequency to a value close to the reproduced clock frequency, it is possible to improve the lock-in of the reproduced clock after the spindle servo is locked or the random access command is released.

Again in FIG. 2, the audio output section has a pair of left and right output terminals 73L, 7 of the analog audio output system.
3R, and a pair of left and right output terminals 74L and 74R of a digital audio output system. Output terminal 73
The audio output from the analog audio demodulation system 14 is supplied to L and 73R. This audio output is LD
During playback, the output terminals 741.
Also supplied to 74R. The changeover switch 75 is, for example,
It is on the a side when D is in the normal state during playback, and is LDD.

When playing a CD, the switch is switched to the b side based on the disc discrimination information from the disc discrimination circuit 10. The audio output from the digital information demodulation system 14 is controlled by the left and right mode lower selector switches 761.76R and selector switches 75L and 75.
R is supplied to output terminal 741.74R.

As a result, during LD playback, the output terminal 73L.

Normal audio signals are output from 73R and output terminals 74L and 74R, and when playing an LDD or CD, high-quality audio signals are output from the output terminals 74L and 74R, and when playing an LDD, normal audio signals are also output from the output terminals 73L and 73R. An audio signal will be output.

The mode changeover switches 76L and 76R are provided to change over the output mode of digital audio audio signals in an analog stage. In other words, if the audio output from the digital audio demodulation system 14 is stereophonic, the above-mentioned output mode will suffice, but in the case of audio multiplexing, for example, the L (left) channel may be Japanese and the R (right) channel may be the same. is in a foreign language, and the mode selector switches 76 operate independently of each other.
By L and 76R, the audio output from the output terminals 741.74R can be switched to three output modes: Japanese and foreign languages, Japanese only, and foreign languages only. The driving of the mode changeover switches 76L and 76R is as follows.
These operations are performed separately according to control information from an operation unit (not shown).

Relays that operate independently are used as the mode changeover switches 76L and 76R. Normally, a relay having one movable contact and two fixed contacts is sufficient for signal switching, but in this embodiment, it additionally has one movable contact and two fixed contacts. A relay is used. That is, to explain the relay 76L on the L channel side as an example, there are two sets of movable contacts 511° 321 that interlock with each other, and these two sets of movable contacts 811, 521.
2 dark blue fixed contacts S 121 provided in pairs for each
13, Sη, and n, the two fixed contacts 5121523 that are the most distant among the two sets of fixed contacts transmit two signals (
It serves as an input end for left and right audio signals), and one movable contact S++ serves as an output end. According to this, since two gaps exist between the left and right signal lines, crosstalk between the left and right signals can be reliably prevented. By increasing the number of contacts and creating more gaps,
Of course, crosstalk can be more reliably prevented.

Although not shown in the figure, a focus servo system that controls the position of the pickup 12 relative to the disk 5 in the direction perpendicular to the disk surface, and a tracking servo system that controls the position of the pickup 12 in the disk radial direction are also naturally provided. Therefore, even in these servo systems, it is preferable to switch the signal processing system for error signals between when playing a video disc (LDD, LD) and when playing a digital audio disc (CD). You can perform a good number board regardless of the type of board.

In addition, the digital signal recorded on CD or LDD is
In addition to audio information, it also includes digitized image information or control information for computer control.

R1111L11 As explained above, according to the recording disk information reproducing apparatus according to the present invention, in addition to the time axis servo using the spindle servo and the buffer 7 memory, tangential navigation is also adopted, so Since the jitter can be suppressed to a certain extent, the jitter of the reproduced digital signal can be reliably removed without increasing the memory capacity, and the error rate can be further improved.

[Brief explanation of the drawing]

Figure 1 shows the frequency spectrum of an RF signal obtained from a recording disk recorded by superimposing a signal obtained by frequency modulating a video signal and an audio signal, and a signal obtained by PCM modulating an analog signal and making it into a pulse. 2 is a block diagram showing an embodiment of the recording disc information reproducing apparatus according to the present invention, FIG. 3 is a block diagram showing a specific circuit configuration of the disc discrimination circuit in FIG. 2, and FIG. FIG. 2 is a block diagram showing a specific circuit configuration of the recovered clock extraction circuit in FIG. 2; Explanation of symbols of main parts 1...Swiss spindle motor 2 for ID and LDD
...CD spindle motor 5...Recording disc 10...Disc discrimination circuit 12...Pickup 14...Digital information demodulation system 15...・・・
・Analog audio demodulation system 16...Video demodulation system

Claims (1)

[Scope of Claims] (1) Demodulation means for demodulating a digital signal included in a reproduced high-frequency signal, and rotation of a recording disk according to a phase difference between a reproduced clock signal included in the reproduced digital signal and a fixed reference clock signal. a first control system that controls the speed; and a second control system that writes the demodulated output of the demodulation means to the memory in synchronization with the reproduction clock signal and reads stored information from the memory in synchronization with a predetermined read clock signal. A recording disk information reproducing apparatus comprising: a third control system for biasing an information reading spot in a track tangential direction of the recording disk based on a synchronization signal included in the reproduction high-frequency signal; A recording disc information reproducing device. (2) The recording disc information reproducing apparatus according to claim 1, wherein the synchronization signal is a reproduction clock signal or a frame synchronization signal included in a reproduction digital signal. (3) The recording disc information reproducing apparatus according to claim 1, wherein the predetermined read clock signal is synchronized with the fixed clock signal. (4) The recording disc information reproducing device is also capable of reproducing a video disc in which a video signal and an audio signal are recorded by frequency modulating (FM) signals and a predetermined digital signal, respectively, and the third 2. The recording disc information reproducing apparatus according to claim 1, wherein the control system performs control based on a horizontal synchronizing signal or a color subcarrier included in a reproduced FM video signal when reproducing the video disc. (5) The recording disc information reproducing apparatus according to claim 4, wherein the predetermined read clock signal is synchronized with the reproduction clock signal.