JPS6171476A - Recording disc information reproducing device - Google Patents

Abstract

PURPOSE:To eliminate the high frequency component of a jitter to which the mechanical system of a tangential servo cannot response by setting the cut-off frequency of a loop filter inserted in the loop of a read clock generation PLL circuit lower than the maximum frequency of the band of the tangential servo loop. CONSTITUTION:Since the mechanical system such as an actuator drive device or the like cannot sufficiently trace the high frequency component of residual jitter even in the tangential servo system, the jitter cannot be eliminated completely. Then in a digital information demodulation system 14, the cut-off frequency of the LPF 32 of a PLL circuit generating the read clock is set lower than the maximum frequency of the band of the tangential servo loop to cut off the high frequency component of the residual jitter thereby eliminating the residual jitter component. More preferably, the cut-off frequency of the LPF 32 is set lower than the warp frequency of a disc (30-8Hz in LDD) so as to eliminate completely also the jitter due to the warp of the disc.

Description

DETAILED DESCRIPTION OF THE INVENTION 1L1 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 A so-called compact disk (hereinafter abbreviated as CD), which is a digital audio disk in which an audio signal is subjected to predetermined digital modulation processing and recorded as a pulse train, is known as a recording disk on which digital signals are recorded. Furthermore, recently, a method has been developed in which a pulse train signal obtained by digitizing an audio signal using a predetermined digital modulation method is superimposed on each FM modulated signal of a video signal and an audio signal (see Japanese Patent Application No. 58-45780). Video discs (hereinafter abbreviated as LDD) have been developed.

In this recording method, the audio signal is converted into two channels, 2.3MHz and 2°8M)-1z.
audio carriers are each FM modulated by two audio channel signals. In addition, the video signal has a sync chip of 7°6MHz, a pedestal level of 8.1M1-1z, and a whitebeak of 9.3. MHz
The frequency is converted so that Then, the audio signal is further converted into PCM (Pulse code Mo.
The signal is digitized and converted into a pulse train signal using a modulation method such as (duration).

This pulse train signal is, for example, an EFM (Eiohtto
The signal is suitable for recording using the Fourteen Modulation (Fourteen Modulation) method, and the frequency spectrum is a frequency component of a pulse train having a width of 3T to 11T. Here, T indicates the bit period of the PCM signal, and a pulse of 3T is approximately 720K)-1z.

The maximum width of the 11T pulse is approximately 200KH1.

Such a pulse train signal is superimposed on the video main carrier at a level of about 1/1o or less, and is slice-amplified near the zero-crossing point to become a pulse-width modulated signal, which is used as a recording signal.

RF (high frequency) obtained from a recording disk on which video signals and audio signals are recorded using the above recording method.
The frequency spectrum of the signal is as shown in FIG. In Figure 1, the component indicated by A is a digitized audio signal component, the component indicated by B is an audio FM signal component, the component indicated by C is a color information component in a video FM signal, and the component indicated by D is a digitalized audio FM signal component. This is a luminance information component.

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, the rotation of the recording disk is phase synchronized with this, and the -H memory is read with a write clock synchronized with the playback clock signal. By reading the written information in synchronization with the read clock, jitter, which is a time axis fluctuation component, is removed.

On the other hand, when demodulating the digital signal extracted from the playback signal by the video playback device when playing the LDD, the playback signal is already synchronized with the reference signal for video synchronization, and the demodulation device in the conventional CD playback device When reading data from memory using a separate reference signal on the PCM demodulation side, the reproduced video signal and the reproduced demodulated audio signal may be shifted in time due to a slight phase shift between the two reference signals. , a blank state may occur due to memory overflow or too much data being read.

Therefore, when developing a playback device that can play both CDs and LDDs, it is necessary to solve the various problems described above when considering sharing the demodulation system for the purpose of reducing costs. .

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned points, and is capable of reliably suppressing the jitter component contained in the reproduced digital signal and producing a jitter-free digital signal, whether playing a CD or an LDD. It is an object of the present invention to provide a recording disc information reproducing device that can obtain the following information.

A recording disc information reproducing apparatus according to the present invention includes: demodulating means for demodulating a reproduced digital signal; writing means for writing the demodulated output of the demodulating means into a memory in synchronization with a reproduction output signal included in the reproduced digital signal; a read clock generation circuit that generates a read clock signal for reading stored information from the memory in synchronization with the reproduced clock signal, and a loop filter for band limitation is inserted in a control loop of the read clock generation circuit. The cutoff frequency of the loop filter is set lower than the maximum frequency of a band of a servo loop that controls the position of the information reading spot on the recording surface of the recording disk in the tangential direction of the recording track. .

Example 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 player that can also play back ordinary video discs (hereinafter abbreviated as LD) on which video signals and audio signals are frequency-modulated and recorded, respectively. This player has a spindle motor 1 for driving the rotation of the LD and LD[) and a spindle motor 1 for driving the rotation of the LD and LD[), since the playback speed is different between the video disc (LD, LDD) and the digital audio disc (CD) as described above.
The rotational drive spindle motor 2 is leaking. .

These spindle motors 1 and 2 are selected depending on the type of disc to be reproduced, and are switched by a switching device 14 using, for example, the motor 3 as a driving source.

In order to detect the disc size of the disc 5 to be played, for example, three detection sensors 6, 7 and 8 are used to detect the disc size of the disc 5 to be played back.
They are provided corresponding to the disk size in the radial direction. The disc size for CDs is approximately 5 inches in outer diameter (
12CIIl) and video discs (LD, LDD).
), there are two types of outer diameter: 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 sent to a disk discrimination circuit 10.
supplied to 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 C01LDO based on the detection outputs of the detection sensors 6.7 and 8.
It is determined which of the three types of discs, LD and LD. This disk discrimination circuit 10
The specific circuit configuration of is shown in FIG. In this figure, C
In the case of D, the disk size is determined to be the minimum (12 cm), and the AND gate circuit 78 generates the detection output of the innermost detection sensor 6 and the inverted output of the detection sensor 7.8 after passing through the inverter 79.80. The output becomes CD discrimination information. That is, when the detection sensor 6 is on and the other detection sensors 7.8 are off, it is determined that it is a CD. For video discs, the disc size is 8 inches and 1 inch.
2 inches, the detection output of detection sensor 7 or 8 is sent to AND gate circuit 70.7 via OR gate circuit 69.
Each of 1 - becomes human power. Further, a frame synchronization detection signal generated when a frame synchronization signal is detected from a frame synchronization detection circuit 21, which will be described later, becomes a low input of an AND gate circuit 71, and is inverted by an inverter 72 to perform an AND operation.
It also serves as a low input for the gate circuit 70. And detection sensor 7
Or, when the detection output of 8 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. be done. 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 carried by a slider base (not shown) which is movably provided in the radial direction of the disk 5. It is driven by a drive unit (not shown) consisting of a reduction gear or the like. The read information read from the recording disk 5 by the pickup 12 is converted into a digital signal via an RF amplifier 13 and supplied to an information demodulation system 14, an analog audio demodulation system 15, and a video demodulation system 16, respectively. The RF amplifier 13 has a wide b":f) range of approximately 5KHz to 14M1-1z, and can reproduce PCM audio A-signals,
It is possible to amplify the reproduced FM audio signal and the reproduced video demodulation system.

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 0, the signal processing system of the reproduced digital signal changes to the A side in the case of an LDD, and to the B side in the case of a CD. When playing a CD, the reproduced RF output is PCM audio information, and this PCM audio information is converted into MTF (Modula
tionTransfer Function) compensation is applied.

On the other hand, in the case of LDD, FM71-dio information and F
PCM audio information, which is present in the reproduced RF signal together with the M video information, is extracted by an LPF (low pass filter) 19 and supplied to a de-emphasis circuit 20. PC
M 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 FM-modulated.
Since the video signal is interfered with by the low frequency components, the low frequency components are boosted and recorded. Therefore, during reproduction, the de-emphasis circuit 20 performs compensation by dropping the low-frequency components boosted during recording. This makes it possible to improve the S/N ratio of the digital signal with respect to 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.
A similar effect can be obtained by using 10FF.

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 written into a memory 24 such as a RAM (Random Access Memory) under the control of a memory controller 25, but at this time, the memory controller 25 is synchronized with the write clock, which is the frequency-divided output from the frequency divider 26 of the reproduced clock. and perform penetration.

Reading of stored information from the memory 24 is performed in synchronization with a read clock obtained by dividing the oscillation output of a vCO (voltage controlled oscillator) 27 in a PLL (phase locked loop) circuit by a frequency divider 28. It has become. 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 frequency 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 LPF.
32 output voltage and the reference voltage Vref+ are selectively set to V.
It is constituted by a changeover switch 33 that supplies CO27.

In the PLL circuit, the change-over switch 33 is set to the a side to set the output voltage of the LPF 32 during LDD playback based on the discrimination result of the disc discrimination circuit 10 described above, and is switched to the b side to set the output voltage of the LPF 32 to the reference voltage Vref + eV during CD playback.
Supply cO27. As a result, during LDD playback, the readout clock for reading stored information from the memory 24 is phase-synchronized with the playback clock by the PLL circuit, and during CD playback, the loop switch 59, which will be described later, is turned on (opened) and the phase comparator The output of 31 passes through LPF77 to CD rotation drive spindle motor 2.
By driving the regenerating clock, the phase of the regenerative clock is 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.

35R to become left and right playback audio outputs.

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
In accordance with the information indicating the usage status of the memory 24 from the memory controller 25, a positive control voltage is applied when the memory 24 becomes overflow D-, and a negative control voltage is applied when the memory 24 becomes blank. The frequency of the read clock is controlled by superimposing it on the output voltage of the LPF 32 and supplying it to the CO 27 via the changeover switch 33.

In this way, the 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 cause the PLL circuit to deal with the problem. By making this request, the memory 24 can always be maintained in a normal state.

In the analog audio demodulation system 15, the outputs of BPFs (band pass filters) 37L and 37R that pass only 2.3 MHz and 2.8 MHz audio carrier components from the reproduced RF signal are sent to FM demodulators 38L and 38R.
FM demodulation is performed in the de-emphasis circuit 39L.
, 39R as left and right playback audio outputs.

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 compensation n is performed in the compensator 44. This dropout compensator 44 includes, for example, a dropout sensor (an analog signal turned off by a detection output of DO8>46) that detects dropout based on a reproduced RF signal supplied via an HPF (bypass filter) 45. It consists of a switch and a hold capacitor provided between the switch output terminal 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. The output signal from the dropout compensator 44 becomes a 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 four phase comparators 48°, and the phase difference with the reference signal output from the reference signal generator 50 is detected. The output of the phase comparator 48 serves as an input to the adder 5.1, and the output of the phase comparator 49 serves as another input to the adder 51 via an equalizer amplifier 52. The output of the adder 51 drives the LDD and the spindle motor 1 for driving the rotation of the LD via an equalizer amplifier 53 and a driver 54. This is the spindle servo system. Further, the output of the equalizer amplifier 52 is connected to a loop switch 55,
An actuator (not shown) built into the pickup 12 is driven via the changeover switch 56 and the driver 57.

By driving this actuator, the optical spot for reading information is moved in the tangential direction of the recording track of the disk. This is the tangential mechanical base. It may also be a tangential mirror that shifts the light spot for reading information in the direction tangential to the recording track of the disk, or it may be a tangential mirror that shifts the light spot for reading information in the direction perpendicular to the optical axis. It is also possible to have a structure in which the angle is biased in the tangential direction of the recording track of the disk.

The loop switch 55 is turned on (opened) 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, first, the spindle motor 1 is driven by the output of the phase comparator 48, and coarse adjustment of the time axis (spindle servo) is performed.
When the locking of the spindle servo is substantially completed, the loop switch 55 is turned on, and the actuator is driven by the output of the phase comparator 49 to perform fine adjustment of the time axis (tangential mebo).

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

However, even in the Tangential Schalmiebo group, regarding the high-frequency component of residual jitter, the actuator drive
Jitter cannot be completely removed because a mechanical system such as an M-structure cannot follow it sufficiently. Therefore, in the digital information demodulation system 14 described above, the cutoff frequency of the LPF 32 of the PLL circuit that generates the read clock is set lower than the maximum frequency of the band of the tangential servo lube to cut the high frequency component of the residual jitter. This makes it possible to remove residual jitter components. More preferably, by setting the cutoff frequency of the LPF 32 lower than the disk eccentricity frequency (30 to 8)-1z in the case of an 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 (LDD, 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 which is turned on (open) during CD reproduction and the driver 60. Conventionally, the above-mentioned tangential rise 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, HPF6
The high frequency component of the time axis error signal extracted by 1 is
A servo that drives the actuator in the pickup 12 via a changeover switch 56 and a driver 57 also employs a tangential servo. Side a when playing an LD, side B when playing a CD.
Switch to the side.

Although the tangential servo during CD playback is performed based on the divided output of the reproduced clock extracted by the reproduced clock extraction circuit 23, Even if it is performed based on the frequency output, the same effect can be obtained since the frame synchronization signal and the reproduced clock are in a synchronous relationship.

The output of the spindle lock detection circuit 58 is connected to the inverter 62.
The signal is inverted at , 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 information 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, a phase difference with the oscillation output of a VCO (voltage controlled oscillator) 66 is detected, and the phase difference signal is supplied to the VCO 66 via an LPF 67 and a 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 reference voltage Vrefz to the VCO 66.

That is, when the spindle servo is not in the locked state or when the information reading light spot jumps tracks due to random access commands such as scan, search, jump, etc., the reference voltage ref2 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 hasten the lock-in of the reproduced clock after the spindle servo is locked or the random access command is released.

Referring again to FIG. 2, the audio A output section includes a pair of left and right output terminals 73L and 73R of the analog audio A output system.
A pair of left and right output terminals 74L and 74R of a digital audio output system are provided. Output terminal 73L,
The audio output from the analog audio demodulation system 14 is supplied to 73R. This audio output is output to output terminals 741.74 via the changeover switch 75 during LD playback.
It is also supplied to R. The changeover switch 75 is located on the a side when playing an LD, for example, as a normal state.

During CO playback, 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 thread 14 is controlled by the left and right mode changeover switches 76L, 76R and changeover switches 751.75.
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. A mode selector switch 76L that is in a foreign language and operates independently of each other;
76R allows the audio output from the output terminals 741.74R to be switched to three output modes: Japanese and foreign languages, Japanese only, and foreign languages only. The mode changeover switches 76L and 76R are driven separately according to control information from an operation section (not shown).

Relays that operate independently are used as the mode changeover switches 76L and 76R. Normally, a relay with one movable contact and two fixed contacts is sufficient for signal switching, but in this embodiment, a relay with one movable contact and two extra fixed contacts is used. is used. That is, if we take the relay 761 on the L channel side as an example, there are two sets of movable contacts 8 that interlock with each other.
11°821 and these two sets of movable contacts SI1. Two sets of fixed contacts 512.13 provided one pair for each S21
, Sη, 23, the two fixed contacts SI2.823 that are the most distant among the two sets of fixed contacts serve as input ends for the two signals (left and right audio signals), and one movable contact S
I+ is the output terminal. 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. Of course, crosstalk can be more reliably prevented by increasing the number of contacts and providing more gaps.

Although not shown in the figure, a focus servo system that controls the position of the pickup 12 relative to the disk 5 in a 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), depending on the type of disc being played. Good servo can be performed regardless.

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.

11. As explained above, according to the recording disc information reproducing apparatus according to the present invention, the cutoff frequency of the loop filter (LPF32) inserted in the loop of the read clock generation PLL circuit is adjusted by adjusting the cutoff frequency of the loop filter (LPF32) of the tangential V servo lube. Since the frequency is set lower than the maximum frequency of the band, it is possible to remove high-frequency components of jitter that the mechanical system of the tangential servo cannot respond to, reliably suppressing jitter components included in the reproduced digital signal, and adding Since phase-synchronized read clocks are obtained, jitter-free PCM demodulation is possible.

[Brief explanation of the drawing]

Figure 1 shows the frequency spectrum of an RF multiplied 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...Spindle 7-tater for LD and LDD 2...
...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)

[Claims] A recording disc information reproducing apparatus capable of reproducing a recording disc on which a video signal and an audio signal are recorded by superimposing a frequency-modulated signal and a predetermined digital signal, the demodulating means demodulating the reproduced digital signal;
writing means for writing the demodulated output of the demodulating means into a memory in synchronization with a reproduced clock signal included in the reproduced digital signal; and generating a read clock signal for reading stored information from the memory in synchronization with the reproduced clock signal. A read clock generation circuit is provided, and a loop filter for band limiting is inserted in the control loop of the read clock generation circuit, and the cutoff frequency of the loop filter is set to a frequency that is determined by the frequency at which information is read on the recording surface of the recording disk. A recording disk information reproducing device characterized in that the frequency is set lower than the maximum frequency of a band of a servo loop that controls the position of a spot in a direction tangential to a recording track.