JPS6171474A - Recording disc information reproducing device - Google Patents

Abstract

PURPOSE:To use the circuit of a demodulation system for a digital signal in common by generating a read clock to read storage information from a memory in synchronizing with a fixed reference signal at CD reproduction and in synchronizing with a regenerated clock signal at LDD reproduction. CONSTITUTION:A changeover switch 17 switched depending on the kind of a reproducing disc is provided in a digital information demodulation system 14, and the switch 17 is thrown to the position (a) at LDD and thrown to the position (B) and CD based on the disc information from a disc discrimination circuit 10. The high frequency band of the frequency characteristic is compensated especially by an equalizer 18 in the PCM audio information at CD reproduction. On the other hand, in case of LDD, the PCM audio information included in a reproduced RF signal is extracted by an LPF 19 together with the FM audio information and the FM video information and fed to a de-emphasis circuit 20. The compensation recording is executed. Thus, the S/N of the digital signal is improved to a low frequency noise at recording and reproduction.

Description

DETAILED DESCRIPTION OF THE INVENTION 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 flAm). Video discs (hereinafter abbreviated as LDD) have been developed.

In this recording method, the audio signal is converted into two channels, 2.3 MHz and 2.8 MHz.
audio carriers are each FM modulated by two audio channel signals. Further, the video signal is frequency-converted so that the sync tip is 7°6 MHz, the pedestal level is 8.1 MHz, and the white beak is 9.3 MHz. Then, the audio signal is further converted into PCM (Pulse Code Module).
The signal is digitized and converted into a pulse train signal using a modulation method such as cation).

This pulse train signal is, for example, EFM (Eighatto).
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 3T pulse is approximately 720KI-1z.

The maximum width of 117 pulses is approximately 200K)-12. Such a pulse train signal is superimposed on the video main carrier at a level of about 1/10 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. It is a plausibility 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,
In contrast, by synchronizing the rotation of the recording disk in phase and reading out the information once written to the memory using a write clock synchronized with the reproduction clock signal, the jitter, which is a time axis fluctuation component, can be eliminated. It is configured to remove.

On the other hand, when demodulating the digital signal extracted from the playback signal by the video playback device when playing back the LDD, the playback signal is already synchronized with the reference signal for video synchronization, and the demodulation in the conventional CD playback device When reading data from memory using a separate reference signal on the PGM demodulation side, as in a device, a slight phase shift between the two reference signals may cause a time lag between the reproduced video signal and the reproduced demodulated audio signal. This will result in

Therefore, when developing a playback device capable of playing back both CDs and 100s, it is necessary to solve the various problems described above when considering the use of a demodulation system for the purpose of cost reduction.

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned points, and it is possible to reliably suppress the jitter component contained in the reproduced digital signal to produce 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 be obtained.

A recording disk information reproducing apparatus according to the present invention includes a demodulating means for demodulating a reproduced digital signal, a writing means for writing a demodulated output of the demodulating means into a memory in synchronization with a reproduced clock signal included in the reproduced digital signal, and a write 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. Clock generation means for generating a read clock signal for reading out stored information from the C.
The present invention is characterized by comprising means for prohibiting phase synchronization by the phase synchronization means of the clock generation means and fixing the frequency of the read clock signal when reproducing D.

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

FIG. 2 is a block diagram, not 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 LDD, and a spindle motor 1 for driving the rotation of the LD and LDD, since the playback speed is different between video discs (LD, LDD) and digital audio discs (CD), as mentioned above.
A spindle motor 2 for rotational driving is provided.・
These spindle motors 1 and 2 are selected depending on the type of disc to be reproduced, and are switched by, for example, a switch 1'A 114M 4 using the 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 disk size for CO is approximately 5 inches (1 inch) in outer diameter.
2c+n), and in the case of video discs (LD, LDD), there are two types of outer diameter: 8 inches and 12 inches. The respective outputs of the three detection tips FJ6, 7 and 8 are waveform-shaped by a waveform shaping circuit 9 and then supplied to a disk discrimination circuit 10. For example, an optical sensor is used as the detection sensor, but the sensor is not limited to this.

The disc discrimination circuit 10 determines whether the disc to be played is a CD or L'D 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 a CD, the disc size is determined to be the minimum (12 cm),
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 after passing through 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 is passed through the OR gate circuit 69 and becomes the output of each of the AND gate circuits 70 and 71. Further, a frame synchronization detection signal generated when a frame synchronization signal is detected from a frame synchronization detection circuit 21 to be described later becomes an input power of the AND gate circuit 71, and is inverted by an inverter 72, and is inverted by the AND gate circuit 70. It also becomes human power. When the detection output from the detection sensor 7 or 8 is generated and the frame synchronization detection signal is input, the AND gate circuit 71 outputs DO discrimination information, and when the frame synchronization detection signal is not input, the AND gate circuit 70 LD discrimination information is output from. 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) that is movable in the radial direction of the disk 5, and the slider base is driven by a slider motor, a reduction gear, etc. driven by a mechanism (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. The RF amplifier 13 has a wide band of approximately 5KH2 to 14MH2, and a single amplifier can amplify a reproduced PGM 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 according to the type of disc to be played back.
5, this switch 17 is the disk discrimination circuit 1 mentioned above.
Based on the disc information from 0, it switches to the A side in the case of an LDD, and to the B side in the case of a CD. That is, L.D.
The signal processing system for the reproduced digital signal is switched between D playback and CD playback. When playing a CD, the playback RF output is PGM audio information, and this PC
The M audio information is M Tl: (Modulation
Transfer Function>Compensation is applied.

On the other hand, in the case of LDD, FM7J-dio information and F
PCM audio information included 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 converted directly into an FM-modulated video signal during recording, the digital signal component will be FM-modulated.
Since this will be interfered with by the low frequency components of the video signal, 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 the memory controller 25, but at this time the memory controller 25 is synchronized with the write clock, which is the frequency-divided output of the reproduced clock frequency divider 26. Write.

Reading of stored information from the memory 24 is performed in synchronization with a read clock obtained by dividing the oscillation output of the CO (voltage controlled oscillator) 27 by a frequency divider 28 in a PLL (phase locked loop) circuit. It looks like this. 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 that uses the divided output from the frequency divider 27 of the oscillation output of 7, an LPF (low-pass filter) 32 that 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 changeover switch 33 is set to the a side to change the output voltage of the LPF 32 during LDD playback, and is switched to the b side to set the reference voltage Vref+ to ■C during CD playback, based on the discrimination result of the disc discrimination circuit 10 described above. ○
Supply to 27. As a result, the read clock for reading stored information from the memory 24 during LDD playback 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 that is q'ed 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), information indicating these conditions is sent 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 of 1 m 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 supplying the output voltage of the LPF 32 to the VCO 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 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, the output of a BPF (band pass filter) 371.37R that passes only 2.3 MHz and 2.8 MHz audio carrier components from the reproduced RF signal is sent to the FM demodulators 38L and 38R.
FM demodulation is performed in the de-emphasis circuit 391.
．． 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 included in the reproduced RF signal and 2.3 MHz to 12.8 MHz during LDD reproduction
The audio 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 passed through a dropout compensator (D
QC) 44, in which dropout complementation is performed. This dropout compensator 4
4 is, for example, an analog switch that is turned off by the detection output of a dropout sensor 1 (DO8) 46 that detects a dropout based on a reproduced RF signal supplied via an HPF (bypass filter) 45; It is composed of a hold capacitor provided between the switch output end and the base t\ 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 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 phase comparators 48 and 49, 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 51, and the output of the phase comparator 49 supplies the equalizer amplifier 5.
2 to the adder 51. The output of the adder 51 is the equalizer amplifier 53 and the driver 5.
4, the spindle motor 1 for driving the LDD and 10 rotations is driven. This is the spindle servo system. Further, the output ◆ of the equalizer amplifier 52 drives an actuator (not shown) built into the pickup 12 via a loop switch 55, a changeover switch 56, and a driver 57.

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 a tangential servo system. Note that the actuator may be a tangential mirror that deflects the optical spot for information reading in the direction tangential to the recording track of the disk by rotating, or it may be a tangential mirror that deflects the optical spot for information reading in the direction tangential to the recording track of the disk, or it may deflect the lens in the direction perpendicular to the optical axis. It is also possible to have a configuration in which the information reading light spot is shifted in the tangential direction of the recording track of the disk by displacing the information.

The loop switch 55 is turned on (opened) in response to a spindle lock signal output from the spindle lock detection circuit 58 when the 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 spindle servo is almost completely locked, the loop switch 55 is turned on and the phase comparator 49 is turned on.
The actuator is driven by the output of , and fine adjustment (tangential adjustment) of 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, the high frequency component of residual jitter cannot be completely removed because the mechanical system such as the actuator drive mechanism cannot sufficiently follow it. Therefore, J is added to the digital information demodulation system 14 described above, and P is used to generate the read clock.
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 were performed based on the horizontal synchronization signal, the same effect could be obtained by performing the spindle servo and tangential servo based on the 3.58 MHz color subcarrier included in the reproduced F to 1 video signal. It will be done.

The above is a servo system when playing a video disc (100, 10>), but when playing a CD, spindle servo is performed based on the output of the phase comparator 31 in the digital information demodulation system 14 mentioned 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 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, HP F
A servo, that is, a tangential servo, in which the high frequency component of the 17!7 axis error signal taken out by the 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 switched to the a side when playing back a DO or LD, and to the b side when playing a CD, based on the discrimination result of the disc discrimination circuit 10.

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 based on the frequency output, the same effect can be obtained because the frame synchronization signal and the reproduced clock have the same relationship.

The output of the spindle lock detection circuit 58 is connected to the inverter 62.
When the spindle servo system is not in the locked state, the spindle unrotator signal is output by the OR gate and W163.

As another input to 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. The OR gate circuit 63 also receives L[)D information output from the disk discrimination circuit 10.

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 on the a side and supplies the output of the LPF 67 to the VCO 66, but the control command described above is
When a command signal is output from 164, it switches to the b side after 6 troughs to this command signal and sets a predetermined reference voltage ■rel.
'z is supplied 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 a random access command such as scan, search, or jump, the reference 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 hasten the lock-in of the reproduced clock after the spindle 1 nerve is locked or after the random access command is released.

Referring again to FIG. 2, the audio output section includes: - A pair of left and right output terminals 73L of the analog audio output system;
73R and a pair of left and right output terminals 741.74R of a digital audio output system are installed. Audio output from the analog audio demodulation system 14 is supplied to the output terminals 73L and 73R. This audio output is sent to the output terminal 74 via the selector switch 75 during LD playback.
It is also supplied to L and 74R. For example, the changeover switch 75 is set to the a side when the LD is being played back as a normal state.

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 left and right mode changeover switches 76L, 76R and changeover switches 75L, 75.
It is supplied to output terminals 74L and 74R via R.

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

Normal audio signals are output from 73R and output terminals 7'4L and 74R, and high quality audio signals are output from output terminals 74L and 74R during LDD and CD playback, and also from output terminals 73L and 73R during LDD playback. A normal 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, if the left) channel is Japanese and the R (right) channel is /-Mode changeover switch 76 whose language is in a foreign language and which operate independently of each other.
By L and 76R, the audio output from the output terminals 74L and 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 76m and 76R. Normally, a relay with one movable 0J 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. To explain the L channel side relay 761 as an example, there are two sets of movable contacts S11°S21 that interlock with each other, and these two sets of movable contacts SI1. S21
Two sets of fixed contacts SI2. +
3, Sn, 23, and the two fixed contacts 312. which are the farthest apart from the two sets of fixed contacts. S23 serves as an input end for two signals (left and right audio signals), and one movable contact S I+ serves as an output end. According to this, since two gyrep exist between the left and right signal lines, crosstalk between the left and right signals can be reliably prevented. By creating more gaps between the points of contact,
Of course, crosstalk can be more reliably prevented.

Although not shown in the figure, there is also 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. Naturally, in these servo systems, it is preferable to switch between the four signal processing systems for error signals when playing video discs (LDD, LD) and when playing digital audio discs (CD).
Good servo can be performed regardless of the type of disc being played.

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.

As described in detail, according to the recording disk information reproducing apparatus according to the present invention, the read clock for reading stored information from the memory is synchronized with a fixed reference signal during CD playback, and synchronized with the reproduction clock signal during LDD playback. This makes it possible to share the digital signal demodulation circuit, which contributes to lower costs for compatible players, as well as reliably suppresses the jitter components included in the reproduced digital signal. It is possible to obtain a digital signal without

[Brief explanation of drawings]

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...Swiss spindle motor 2 for LD 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)

[Claims] A first recording disk on which a video signal and an audio signal are recorded by superimposing a frequency-modulated signal and a predetermined digital signal, and a second recording disk on which predetermined information is recorded after being subjected to a predetermined digital modulation process and converted into a pulse train. A recording disc information reproducing apparatus in a recorded information reproducing apparatus capable of reproducing a recording disc, the apparatus comprising: demodulating means for demodulating a reproduced digital signal; and a demodulated output of the demodulating means being synchronized with a reproduced clock signal included in the reproduced digital signal. a clock generating means for generating a read clock signal for reading stored information from the memory; a phase synchronizing means for synchronizing the output of the clock generating means with the reproduced clock signal; 2. A recording disk information reproducing apparatus characterized by comprising means for prohibiting phase synchronization by the phase synchronization means of the clock generation means and fixing the frequency of the read clock signal when reproducing the recording disk.